"Omae wa mou shindeiru."
- Kenshiro
"NANI?"
- everyone else
Omae wa mou shindeiru (お前はもう死んでいる) is a Japanese phrase from the anime and manga "Fist of the North Star." Translated into English, it means "You are already dead." It is what the main character, Kenshiro, says when he uses his "Hokuto Shinken" martial art style to kill opponents. He does the anime-blur thing to the opponent, attacking their pressure points, then while they're looking confused or haughty, he says the line, and they have enough time to shout "nani?" ("what?") before they explode. Here's an example, and another.
As far as memes go, it's pretty fuckin' niche and is usually reserved for weebs. Like other memes, it's made its way to Youtube with people editing the quote into other situations involving people getting attacked. Here's a 10 minute compilation video. Here's one with a cat. And Will Smith.
Please note, this is a shitpost-tier, Youtube Poop kind of meme. That is to say, something stupid and random for the sake of being stupid and random, but beyond regular Millennial or GenZ surrealism. This is like the dadaism of Youtube memes. I mean to say that the humor of the Youtube videos is very niche.
There are also image memes, which are muchmoreaccessible.
Also, MGDMT did a comic of it, which I FINALLY understand after all these years, so that's nice.