Dark Leonardo is Leonardo's evil clone created by Sh'Okanabo along with the other Dark Turtles in Fast Forward.

Being a clone of Leonardo, Dark Leo is the leader of the Dark Turtles, Leo tries to talk to him, saying he has to have honor if he's truly his clone. Dark Leo himself admits that he and the other Dark Turtles have many similarities to Leo and his brothers, but says honor and value aren't one of them.

Unfortunately Leonardo was beaten by his dark clone of himself, and then turns to you, an evil and smug look on his face as he turns to you, giant swords in hand.

”And what can YOU do, Pip-Squeak?? You must be a MORON if you’re gonna side with THESE turtles!”