It depends on what you mean by cheating. If you mean has Wade Wilson (aka Deadpool) been unfaithful to a significant other, I don’t think so. But I know the reverse is true. Wade came home to find his wife Shiklah in bed with Werewolf by Night. He was not pleased and expressed that via a shotgun blast.
If you mean cheating in fighting, I have no doubt he’s broken numerous ‘rules of combat’ over the years. The guy is a mercenary/assassin.
He has a moral code but it is loose and didn’t sit easily with Captain America’s ‘no kill’ rules while they were fellow Avengers.