I don't think it has been mentioned, but: Premium tanks in World of Tanks.
Pay2Win in general is utter cancer, microtransactions are a desaster, but holy fucking shit, is it ridiculous when it comes to the tiered combat system of WoT.
Tanks get put into tiers depending on how effective they are in their role, but to make pay2win tanks more interesting, they are not only superior in all regards to a comparable tank of the same role, they are also in comparatively low tiers. Essentially, you're the games designated seal-clubber. Add to that the Russian bias that makes Tigers light up like Zippos with weak-ass armor and heavily reduced armor penetration and you get a mess of a game.
That being said: Bias on part of the game makers was a bitch, too.
Some years ago, one of the KV-variants, I think the KV-1S, was so incredibly overpowered for its tier, it was literally "The other side has one of those? Well fuck us, I guess." Barely anything could hurt that fucker, even from the sides, its cannon shot quickly, it penetrated anything and it did a metric ton of damage. It was ridiculous... and people complained for months before the devs reacted: They promised to put the tank into a higher tier "soon", but did sweet fuck-all for 2 or 3 months... meanwhile, they merrily introduced new tanks into existing techtrees of the other nations that ended up pushing everything after those new tanks up a tier and thus fucked them over even harder. I think when they finally changed the KV-1S into a higher tier, every other tank in that tier had already been nerfed.
Something specific to that game: Pseudo-historical tanks that never existed.
The game is choke full with tanks that were designed, planned or even just suggested during WW2, which makes some nations end up with utterly retarded designs that would never work, but since the game uses the crazed fever dreams of war-stressed Generals as foundation for their capabilties, you end up with tanks that drive faster than anything in their weight bracket, cause unlike the real tanks, that needed to come up with a propulsion system based on what's actually available, some General going "Yeah, we'll find a 1500HP engine of the correct size and weight somewhere, I guess..." Same with the armor and guns. Essentially, you end up with a tank that never left the most basic design phase, never had been put together to see if that shit even works and sometimes uses experimental technology that you'd not see employed up to this date to this degree.
The result: A tank with a ridiculously low weight, but a ridiculously strong engine, nearly unbreakable armor and a quick-firing gun that blows chunks out of tanks 20 tons heavier and 3 tiers higher without any problems. And this fucker costs 50 bucks. Never mind the whole thing would need to be build with armor as light as styrofoam and as sturdy as diamond to be able to even pull off half of this shit. Never mind that the engine would have to be so utterly large, it would fill up the entire insides of the tank and leave no room for crew or ammo...
And that abomination goes against some upgraded Panzer IV with all its historically existing specs (implemented by biased slavs)...
We used to call these made up tanks "sketch-tanks" or "napkin tanks", cause quite a lot of those felt like Hitler, Churchill or DeGaul had doodled them on a napkin while eating and going "This! I want this!".