Mr Mxyzptlk is back, but he won’t be able to stop Deadpool! Deadpool has his healing factor and his guns at the ready. Mr Mxyzptlk will have a hard time trying to deal with all of that. He definitely likes making tricks, but Deadpool always manages to get the last laugh. Deadpool wins.
Update! As of 07/11/2016 It has been pointed out that Mr. Mxyzptlk aqctually has had some decent moments and feats in the comics with serious firepower. I don’t think Deadpool will be able to keep up with this guy. Mr. Mxyzptlk wins.