Jimmy Kimmel. He had to get his goons to do their mobster shtick and drew more attention onto Kimmel's criticisms of him. Over half of America wouldn't even know what was in Kimmel's monologues except Trump himself has shown a spotlight on them.
A normal president would've just walked up the escalator stairs, made a good-natured joke about it (maybe asked in private what happened) and that would've been that. No, no, instead he has to make it a week long grievance, complete with threats of firings and prosecution and whatever else this addled old fart thinks of in the moment. It's insane that this is our reality. We were once the most powerful country in the world, highly respected, now we're a pathetic joke because our whiny bitch baby has to have a tantrum once a week.