This quote is associated with Resident Evil 4, the 2005 survival horror game that became hugely popular across consoles and PC. Spanish enemy voice lines from the Ganados were especially memorable, and "Detras de ti, imbecil" spread online through gameplay videos, meme compilations and streamer reactions. It remains popular because the meaning is instantly clear even to many nonplayers: someone is in danger and does not realize it yet. That makes it useful well beyond Resident Evil edits.