For me it was Terraria, Satisfactory, Tetris Effect Master Mode, Minecraft with Mekanism mod & CSGO / CS2 (almost 2000 hours in CS alone).
Edit: There are so many answers that I might only reply if I have something interesting to say. I will read all of your answers though. 🙂
Edit 2: It has become too much for me and I have to disable notifications. Thank you for the massive response and please continue to discuss with everyone here. ❤️ 🫡
Rocket league. Scrolled all the comments and slightly disappointed to not find this one :/
This was a game I was truly addicted. Uninstalled it many times recognising it as an addiction but kept coming back to it. I feel lucky that I could break out of it. It was THAT addictive. Around 1200-1300hrs on that game.