Game Breaker / Heroes of the Storm

A few characters have been accused of being Game Breakers, particularly throughout the alpha and beta.
  • Healing was considered this early during the beta, when one team had a healer and the other didn't — teamfights are a big part of matches on smaller maps and especially PvP games and the ability to recover more easily/get healing within them was seen as a major advantage for the team with a healer. Less complaints have been seen since then.
  • Every character's been accused of this at some point or another, but special mention must be given to Nova (whose combination of stealth, range, and fast/high damage can destroy unprepared teams, killing players almost before they can react in some cases) and Abathur (who's difficult to play, but very effective, particularly against teams who haven't figured out how he operates) towards the end of the alpha. Blizzard responded to this by nerfing both of them into Tier-Induced Scrappy status at the beginning of the beta, with Thrall seemingly taking their place as a highly complained-about strong character... then nerfed him to ground while Kael'thas reigns as the king of meta, thanks to his high AoE burst designed to melt down team fights, and apparently, a patch that removed one of his key Talents to do so (Ignite) wasn't enough to bring him down yet. His only contenders so far (overpowered hero release) are just Li-Ming and Xul (see below), but in spite of that, Kael'thas is still sitting on top of the meta throne.
  • Sylvanas is at the top of many tier lists, but in the Haunted Mines map she truly becomes this. Unlike the other maps' "super units" (the Dragon Knights and the Terror), the bone golems in Haunted Mines do not have a time-limited life. Instead, they disappear only when they are killed, which in the case of strong golems is only feasible with the help of towers and forts. Too bad Sylvanas can stunlock said towers and forts, making them unable to damage her team's golem. Many Haunted Mines games have ended after a team with Sylvanas took a good amount of skulls and wielded an effectively unstoppable golem for a Curb-Stomp Battle. Even with Haunted Mines removed from Match Making, Sylvanas is still one of the strongest heroes in the game.
  • Li-Ming has gained this status since her release and is been dubbed the most overpowered hero in the entire game. To elaborate why, she has three abilities: Magic Missle, Teleport, and Arcane Orb. Magic Missle is a very useful poke based attack that is a instant cast and will prioritize hitting enemy heroes when they're near, Teleport allows her to escape fights and with the right talent can allow her to deal damage, and Arcane orb throws out a small orb that increases in size, is fast, and if it hits it stuns and knocks you up for a second. Her passive abilitiy though automatically refreshes all her cooldowns with a kill. Think about that for a second. Making this even worse is how one of her heroics, called Disintegrate, is a ridiculously fast and power Kamehame Hadoken. A Li-Ming player can kill most heroes with simply combing Magic Missiles, Arcane Orb, and Disintegrate. Her two primary weaknesses are her abilities using up a lot of mana and her being a Squishy Mage but both are easily manageable as she gets very power talents that can increase her mana regeneration by 100% if she's below half mana. Her talents all increase various parts of her abilities, including allowing Teleport to deal upwards of 500 damage for being near when she hits her spot or, the one players most hate, is her talent Ess of Johan, which makes Arcane Orb, when it damages a enemy, drag the enemy to the center. All of these, combined with her ability to spam heroics when no other hero can, has made her seen as the most broken hero in the games history right after Kael'thas. Li-Ming was so broken in fact, that Blizzard's Nerf for her in the Patch Notes out right states she was "a little too strong right now" and reduced many of her most game breaking talents, with Ess Of Johan being outright removed as well (much like Kael lost his Ignite). However, she looks less broken with the release of Tracer, not because she got nerfed, but simply because Tracer counters her. Hard.
  • Xul is pretty much what every overpowered hero wishes they could be. He's capable at doing almost everything, being durable enough to take a lot punishment with his Bone Armor and a health pool almost equivalent to Anub'arak's, able to push down waves and forts quickly due to the combination of his spells and passive, and having the damage and crowd control to contribute to ganks and fights very well. That's all combined with very varied and great talents that allow him to be extremely flexible with his builds. Even with his notable flaws, such as a lack of escape and gap-closers and his reliance on his team to get his spells off and fight effectively, he very quickly climbed to the top during the week of his release, and, as of this writing, has the highest winrate in the entire game, with his most popular builds maintaining above a 70% winrate and climbing. His nerfs two weeks after his release, which brought him more in line with the other heroes without making him useless, were well received by the fanbase.
  • Post-rework, there was only one support considered Viable. His name is Rehgod. Imediately after the rework, Rehgar had high damage, healing, crowd control, mobility, pushing, and durability, making the entire support class (And to some degree, the warrior class as well) obsolete by comparison. Blizzard spent an entire month nerfing him patch after patch, and he only left the meta after they stopped him from casting his Ancestral Heal on himself.
  • Kael'Thas is one of the top Assassin heroes thanks to his multiple Herd-Hitting Attack spells, in a game that emphasizes team brawls. Get too close to each other when his spells go off, and you'll infect your teammates with Living Bomb, make his Flamestrike deals 8% maximum hp damage bonus (particularly painful for tanks, doubly worse if the Flamestrike is talented to explode twice), and his Phoenix dealing way more damage than it deserves. There's been patches that both buffed and nerfed him, but he remains one of the top tier Assassin heroes. The Dev Notes also lampshade it in one of the patches:
    Patch Notes: We’re a little uncomfortable with how much single-target burst damage Kael’thas is able to put out with Sun King’s Fury, so we’re toning it down. He threw a fit about it, but we’re sure he’ll manage to find some other way to be a little too powerful. He always does.
  • Samuro can be an absolute terror. He's like a melee-range hybrid of Valla and Nova: the more he hits, the faster he hits and moves; and he can spawn illusory-but-still-damage-dealing copies of himself & turn invisible to escape or position for a kill. If you're sharp, you can tell which of the copies is the real one — it's the one who acts as though his Hit Points matter — but when all three of them literally spawn on top of you, with full HP, in the midst of a teamfight, it can be hard to be that sharp. In the meanwhile, all three of them: get attack- and move-speed buffs every time they hit a hero (which can be strengthened by Talents); deliver Critical Strike (double damage) every few attacks (which can also be strengthened by Talents); and are tangible, meaning they can body-block you into a corner. He will almost certainly be nerfed, hovering at a 62% win-rate as of this writing.
  • Overwatch characters in general can be somewhat problematic. Where the Diablo universe focuses on Stone Walls, StarCraft on Glass Cannons and WarCraft on Mechanically Unusual Fighters, Overwatch specializes in Fragile Speedsters; more than half of them have at least one enhanced movement ability. That doesn't sound like much of a problem until we start talking about just how prevalent manually-aimed skillshots are in MOBAs, and how valuable mobility is as a result. You can't kill what you can't hit... and most Overwatch characters are very slippery.
  • Malthael saw almost instant success upon release, with his winrate still climbing in spite of nerfs to his key talents. His kit makes him a potent threat that's very hard to escape from without help, and his immense self-sustain means he's nearly impossible to kill when it matters. Not to mention, his percent-based damage and sticky teleport skill counter tanks and high-mobility heroes respectively; two staples of the current meta.
  • Garrosh. Not only is he a generally strong tank, he has one the most punishing kits in the game. His Wrecking Ball is a nightmare for any melee hero. Point, click, chuck an enemy to a target location, usually in the middle of your team or into your fort. The only downsides are its targeting system (it picks the nearest enemy, with no priorities over heroes) and its puny grabbing range. The first problem can be alleviated by not fighting in lane, and the second is automatically made up for with Groundbreaker. While Groundbreaker is a pretty narrow skillshot, all you have to do is land it once to score a free kill. Compared to fellow displacement tanks Artanis and Stitches, Garrosh has less risks and is far less telegraphed, while also having the most rewarding displacement of the three. It's a nightmare to deal with.
http://tvtropes.org/pmwiki/pmwiki.php/GameBreaker/HeroesOfTheStorm