Now I do not mean strongest playable character. I mean who has the most kills world wide life time across all games they are in. Mario for example does not look scary but if you added all the Mario kills for his lifetime across all games, all playthroughs worldwide, he is a terrifying world ender.

Edit to clarify Every kill from every player ever. In all games, the character is in. So add a kill to Mario every time someone stomps the first Goomba in Mario one world wide. That means time a game has been played is a big factor.

Edit 2: While I realize I could have written the post better, I have really enjoyed reading the responses, I even found a few games I want to check out. Thanks, everyone.