For me it's Diablo II. Granted I've played my fair share of D2 since launch, and also recently on a private server with a comrade from hexbear, but I still feel like years later the game didn't grab me as much as D1 did.
Granted I don't hate D2, but for a game that I keep coming back to, D1 takes the prize.
Overwatch 2. How they fucked up the maps, the matching, the ranking system are all case studies on how to not make a sequel.
But that's not the worst fucking part that shocks me.
The worst part that shocks me to this day, is how they got me to actually miss loot boxes.
They fucked up with the prices for skins and hid all the semi valuable stuff behind a season pass that is always 20$.
I'm not paying ~1/4 the price of an entire AAA game for one season pass.
They didn't even put the coolest skins in the season pass, those are like 10-15$ on their own.