Killer King?????

It is a tough achievement to get, but you get it by moving the King for a discovered attack checkmate or by castling checkmate (both are unlikely situations to come up).
I've had several games I've won by castling checkmate or discovered attacks by a King move, but I also play a lot of chess too If you REALLY wanted this award, you could also try to engineer this ending by playing a weak bot in live chess; this also gets the achievement.

Check out this #chess game: BraveBeaver1 vs payamshahsavaribaboukani - https://www.chess.com/live/game/81452513452