Game Breaker/Team Fortress 2

Yes, Team Fortress 2 had enough items believed to be a Game Breaker that it needed its own page.

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• First off, the Sandman, introduced in the Scout update. This unlockable replacement for the bat tosses a baseball that stuns the foe (and until an update several months after its release, even in Über Charged state) for 8 seconds. And after stunning someone, you can pick up your ball (or someone else's) and use it again. It became the first weapon in the game to be banned in league play.
  • In fact, the Sandman caused so much controversy that Valve has nerfed, then buffed, then nerfed it numerous times. Seriously, look at how many patches have been applied to it. In its current state, it sees relatively little use in all types of gameplay, since few players see its benefits as worth taking the health loss.
• How about Natascha? In theory, it was supposed to be weaker because it did less damage per bullet than Sasha, and its "slowdown" effect was meant to make it a support weapon that made it easier for teammates to hit people you were shooting at (or for you to land more bullets on them). In practice, the slowdown effectively become tractor beams, making anyone that been shot ONCE, regardless of distance, become a statue, allow even more shots to be landed. Thus, the second weapon to be banned in competitive leagues. The Australian Christmas update reduced the effect of the slowdown to only work at close range, and increased its spin-up time so that Natascha-wielding Heavies were easier to ambush. So now it's more balanced, and there's less complaining.
• There is the opinion going around that the Demoman is overpowered, citing the fact that his Grenade Launcher can One-Hit Kill four out of nine classes with a direct hit at close range, Stickybombs that do the same thing only with more control, and the fact that there is no class specifically purposed or set up to counter him. He can be countered by smart players, but in lots of situations he can still absolutely dominate the battlefield.
  • This is hilariously (and possibly intentionally on the developers' part) Lampshaded by even the bots themselves. If you play the Offline Practice Mode and put yourself in the spectator mode, watch as the bots slowly realize that they can't get by without a human taking care of the threats, and all switch over to Demoman. The funny thing is, this actually works.
  • Also Lampshaded, and perhaps as a Take That against player complaints about the class, during the Soldier/Demoman War, one pro-soldier promotional image proclaimed "MOST OVERPOWERED ENEMY OF ALL TIME STILL FINDS WAY TO LOSE, COMPLAIN".
• The Equalizer is quite controversial among many circles. As the player loses more and more health, he starts moving faster and deals more damage while it's the active weapon, meaning that it becomes quite possible to one- or two-shot three or more enemies in a period of a few seconds, as the damage lets you kill almost any class from full health in two hits and the speed makes you hard to hit. The flip side is that Medics can't heal you while it's the active weapon, but when you're moving around so quickly and dealing so much damage, why would you want to be healed? As a melee weapon it's limited in how game-breaking it can be, but most players consider this a pure upgrade over the regular shovel, and Valve has spent several patches nerfing it.
• Demoknights (Demomen equipped with a sword and a shield) have become the unquestioned masters of close-ranged combat due to having a fast-charging attack that lets them easily close the distance with their targets and land guaranteed Crits or Mini-Crits, swords that have a much longer reach than every other melee weapon in the game, significant resistance against the only two reliable ways to kill enemies at close range (fire and explosives), and two weapons that allow them to heal quickly and easily in a frantic brawl. If you're close enough for them to hit you and you're not a Heavy, you're pretty much dead. As a Pyro, the only guaranteed way to kill one is by using airblast to stop his movements and then switching to Axtinguisher, but their fire resistance and health-replenishing weapons make using your flamethrower almost completely useless, and they can still use their Grenade Launcher to gib you as you try to close in with the Axtinguisher. They are also fairly unpopular for not really contributing much to the team as a whole, as they are almost completely locked out by any competent Engineer or a diligent Sniper.
• When the Spy vs. Sniper Update came out, the Spy got two new invisibility watches that could (1) let the Spy stay invisible indefinitely, or (2) fake his death and become essentially invulnerable for 6.5 seconds while ignoring the bump-into-reveal-cloak penalty. Not so bad by themselves since they also had significant drawbacks, but at the time of the update, the Spy also got his own taunt kill, which could still be performed while invisible. Valve spent several patches fixing these oversights.
  • The first release of the Dead Ringer let him cancel it immediately. Add the fast recharge and as long as you constantly clicked to keep it active and cancel any faked death, you had about 1200 HP (ten times the normal amount or so). Compare the highest-HP class, the Heavy, with his smashing 300 HP, the Spy was basically immortal until a patch fixed this. Now it drains an extra bit every time you cancel, as well as having a cooldown of sorts.
  • It was still broken when it started draining at cancel, because you could decloak (loudly) right before touching a big ammo box, and then immediately ready it up again. Combine this with the typical player mentality of "kill enemy > capture objective", and you could take an easy MVP on defense with virtually no kills by just being an unkillable pest near the attacking team's spawn. In particular, Gold Rush stage 2 point 2 was virtually impossible to lose because of the abundance of ammo back near point 1. This was eventually fixed by severely reducing the amount of cloak that can be gained from large ammo boxes while holding the watch in question.
• The Sniper's unlockable primary, the Huntsman, also falls into this category for some. You would think that a bow-and-arrow that does less damage than the Sniper Rifle, carries less ammo, has no scope, and is less accurate would be inferior, right? Not if it uses the flamethrower's hitscan box to determine hit detection! Not only is the hitbox for scoring a successful hit on a target at least twice as big as the target when you're using the Huntsman, arrows that fly close enough to the head will score a headshot. Ever wonder why that Sniper that you ambushed from behind was able to suddenly turn around and headshot you at point-blank range? Now you know.
• The Engineer Update set a new standard for turtling. One of the Engineer's new weapons was the Wrangler, which allows an Engineer to take personal control of where his Sentry Gun shoots. Not bad by itself, but consider the fact that this gives the Sentry infinite range (along with the fact that it has no damage falloff, meaning it does full damage at any range), and among the Wrangler's features is that it doubles the Sentry's fire rate (which is is basically double damage), and projects a shield that causes it to take only 33% damage, tripling its HP. With no downside apart from disabling the Sentry for three seconds when the Wrangler is un-equipped or when the Engineer is killed. Instantly banned in competitive play.
  • Among the new features in the same update is the ability for an Engineer to pack his buildings up and move them. Not too bad by itself since it's generally a wise idea to be able to move Dispensers and Teleporter Exits forward as your team advances. But when you can move your Sentry Gun as well, and combine it with the Wrangler... you can take over and lock down an entire area given about six seconds of nobody noticing you.
  • The Engineer can also use the Sentry's knockback to shoot himself into otherwise unreachable locations with the Wrangler (called Wrangler-jumping or Sentry-jumping) and set up nigh-impassible choke points, especially not when supported from traditional Engineer campsites by other Engineers. Additionally, some of these places can still be built on, so it's possible to build a Teleporter Exit that cannot be reached by the enemy team.
• The first Polycount Update (along with Australian Christmas) brought this with the advent of 'set bonuses.' Having an entire set of equipment grants bonuses and flaws on top of existing ones. While bonuses and flaws aren't exactly new, what made it game-breaking is that some of these sets didn't come with any flaws at all, meaning that somebody with the item set hat had a pure advantage over someone who didn't (for instance, a player with the Special Delivery set while wearing the Milkman has 25 more HP than a player without the hat, while carrying the exact same weapons loadout).
  • The Scout's Mad Milk was this for quite some time. Anybody it with milk became an instant HP replenishment sink for anybody who had the common sense to shoot at them, since any damage done to a milk-covered player would return 75% of that amount as health to the attacking player. This meant that if you had a high enough damage output, you could essentially heal yourself almost as fast as a Medic can, without the Medic. Thankfully, this was later toned down to a more reasonable 60%.
  • The Soldier's Battalion's Backup was also this for a time, though for different reasons. You charged it up by taking damage from enemy attacks, and once you get to a certain point, you just let it loose and any teammates close by becomes immune to critical hits (including headshots) and got a 35% damage resistance buff. By itself this wasn't so bad since the effect only lasted for 10 seconds or until the Soldier died (and everybody instantly targets banner-wielding Soldiers as high-priority targets), but the Soldier only had to take 175 damage in order to fully charge it; given that the Soldier has 200 HP by himself, and even more given Medic support or by using the Black Box, it virtually guaranteed that a Medic-backed Soldier could have an active banner going around 50% of the time. The damage requirement was doubled to 350 damage later though, making it somewhat more balanced.
  • In general the first set of Polycount item sets drew a lot of hate and ire since they required players to wear a hat alongside the items, and hats are a hell of a lot harder to come by than weapons, both in random drop and in crafting. So, for the first few weeks of the update (and for months afterwards), the only ones who were able to take advantage of the item set bonuses were the ones that either got lucky in item drops or crate openings, were farsighted enough to save up enough Refined Metal to craft one of the hats before the update, or simply purchased the hat from the Mann Co. Store.
• With the Australian Christmas, another batch of item sets came about. However, out of all the new weapons, the item sets were not as hated (they weren't as good, requiring a huge tradeoff for a minor bonus, on top of not requiring the hat for the set bonus this time around) compared to Heavy's Fists of Steel. Sure, you take double damage when hit by melee weapons (usually resulting in OHKO when engaged in melee battle, especially against a Pyro with the Axtinguisher), but the fact that it provided 60% damage resistance against ranged weaponry allowed Heavies to survive fully-charged headshots, as well as Sentry barrages. Thankfully, this was later reduced to 40% and a weapon switch time penalty was implemented as well.
  • Add on to that the fact that everyone instinctively backpedals and shoots at a melee equipped Heavy usually...
  • At one point, it got bad enough that a Heavy equipped with the Fists of Steel, while backed by a Medic, could wade into Sentry Gun fire on Capture the Flag maps, grab the Intelligence, and simply waltz back out, as the combination of overheal and damage resistance meant that the Heavy had a total effective HP of over 1100, and was being healed for effectively 60 HP/second, just under the fastest rate at which a Medi Gun can normally heal players. The same thing could be done with carts on Payload maps, completely shutting out any push or defense attempts against anything but an Axtinguisher-equipped Pyro.
• The Über Update gave the Heavy the Tomislav, a minigun with a silent and fast spin-up that does slightly more damage than Natascha. In effect, the faster spin-up time turned the Heavy into the most powerful ambushing class in the game, even moreso than the Pyro, who was designed specifically for ambushing enemies, because the slow spin-up time and the loud whirring of the Minigun's barrel were supposed to be the Heavy's greatest weaknesses. Immediately after the update hit, Heavies could sneak up behind their enemies and mow them down effortlessly, to the point that the reduced damage output didn't matter at all. And trying to sneak up on one to perform an ambush was futile, since they could turn around and mow you down half a second after you land your first hit.
  • Another problem was that since it spun up faster, the slower firing speed didn't matter at all since the time saved spinning up could be used to kill most weaker enemies faster (which makes a large difference in the case of a Medic) versus the regular Minigun. A patch which lowered its spin-up time reduction from 75% to 40% has somewhat rectified this.
• The Enforcer was another Über Update weapon that was highly controversial upon release. For a 20% damage increase, its only disadvantage was taking a little extra time to become invisible... something easily negated by using the Dead Ringer, which instantly cloaks regardless. The additional damage allowed Spies to fight on the front lines and deal a surprising amount of damage to pursuers, which completely eliminates the Spy's class disadvantage of not being able to fight back against other classes in a direct fight or when discovered. This got especially terrible when a certain glitch with the Diamondback allowed players to exploit infinite crits with the Spy's primary weapon. However, it has since been nerfed and now only causes the damage bonus when the Spy is undisguised, has a slower firing speed, and can't deal random critical hits.
• Upon initial release, the Cow Mangler 5000 was quite unbalanced. Besides dealing reduced damage against buildings and being unable to land random crits, it had no drawbacks compared to the stock Rocket Launcher; however, it has unlimited (reserve) ammo AND 5 shots per magazine instead of 4, allowing Soldiers to do huge amounts of damage while away from support, and its damage ramp-up was unintentionally too high, meaning that it did more damage than the Rocket Launcher at close range. On top of all this, it has a special charge attack that lands a guaranteed Mini-Crit (which also sometimes did more damage than normal on top of the increased ramp-up), ignites players hit by it, and disables Engineer buildings for 4 seconds; this allowed Soldiers to disable Sentry Gun nests from a distance without the need to get a Spy close-in, and possibly kill the Engineer tanking it. Then there was the fact that it was a literal game breaker in that its particle effects taxed some graphics cards beyond their limits. Virtually all of this has been fixed, and it has slight damage and reload time penalties, so it's fairly balanced now.
• The Machina is this for some. It does an additional 15% damage on a full charge, making it capable of one-shotting anything short of a Soldier or Heavy at full health (with the former it'll leave them at 1 or 2 HP at most) with a bodyshot, which means the Sniper gets a huge boost to his effective hitbox. It's also capable of penetrating enemies on a full charge, meaning a lucky shot can potentially take out a Heavy and kill the Medic who's hiding behind him. It has two downsides in exchange: it fires tracers to tell the enemy exactly where you are, and can't shoot while unscoped. If you're camping in an entrenched position, then neither of these disadvantages matter, and the weapon is a pure upgrade over the regular Sniper Rifle.
• The Heavy's Sandvich was somewhat overpowered for quite some time. One of its functionalities that was added some time after initial release was to use alternate fire that allowed the user to throw it down and have it act as a medium health pack. Not broken on its own since it encouraged players to share their food with their teammates, but this also applied to the Heavy who threw it, allowing him to heal 150 health nearly instantly, which made it virtually impossible to kill a fleeing Heavy (or one wounded inbetween engagements) since they could thrown down their Sandvich and instantly replenish health on the move. Combine this with the Gloves of Running Urgently, and you suddenly have a very mobile Heavy that can get to the front lines for negligible penalties. The devs later removed the self-healing feature, only allowing a Heavy's teammates to pick up the Sandvich for health, while the Heavy must physically eat it in order to regain health.
• The Pyro's Phlogistinator is a fairly controversial weapon. In exchange for having no airblast, Pyros gain a "Mmmph" meter that tracks how much damage the weapon does. Once it's built up enough, they may activate a taunt that gives them guaranteed critical hits for 10 seconds, while restoring them to full HP. Normally, this wouldn't be too bad, but for the duration of the taunt, the Pyro gains 90% damage resistance, essentially making them invulnerable. This allows players to stop in the middle of the battlefield and taunt without any repercussions until after the taunt has finished. Additionally, the required fire damage in order to activate the taunt is a mere 225 points, which is easily achievable in one life (just kill one or two enemies and ignite a couple others), and the critical hit boost is longer than the Medic's Kritzkrieg Über Charge. On top of that, fire damage wasn't limited to igniting enemies with the Phlogistinator, using a flare weapon could guarantee that you would have a full meter before even getting within flamethrower range of an enemy. Thankfully, Valve toned this down by reducing its damage by 10%.
• The Spy-cicle, similar to the Enforcer upon release, is highly controversial for what it does. While the silent killing feature is offset by turning its victims into easily spotted ice statues, the real issue is that if the Spy is set on fire, the Spy-cicle will instantly put the Spy out and make him fireproof for 2 seconds, in exchange for not being able to use it for 15 seconds. This nullifies (or at least drastically reduces) the threat posed to Spies by Pyros, which is supposed to be the Spy's greatest class weakness. When combined with the Dead Ringer, you have a virtually invincible Spy that can't be spy-checked.

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And so on and so forth. Every time an update ships, you can be sure that somebody will be complaining that Metagame has been Ruined FOREVER.