The patch for Battlefield 2, a game by Digital Illusions CE, that completely ruined the game, opening great new possibilities of exploting/cheating and unleashing the entire new dimension of bugs and glitches.
"Holyshit, now it takes me 5 minutes to verify client data instead of 30 seconds and the game crashes to desktop every hour! And those Karkand hotel glitches keep killing me as I pass by... Guess I'll just go back to the lovely CS: Source now. Damn you, 1.3 patch! Damn you patch-making monkeys!"