Characters so powerful and broken they completely dominated their games metas
The Nurse from Dead by Daylight’s very basic ability to teleport means that it compeltely counteracts how the normal game is played, making her absurdly powerful to the point of being broken. The only reason she’s not played by everyone is because she’s a hard killer to master.
The Ice Climbers in Brawl (or maybe melee I honestly forget) had an infinite combo that they could use very easily by desyncing the two characters movements that would practically automatically win them the game if they could pull it off.
Tauros was an unbelievable powerhouse in Gen 1 Pokemon meta that it was literally unthinkable to not have one on your team, along with Snorlax and Chansey. In fact some people try to slot in other Pokemon to just fill in the role as a second Tauros.