Worst Intern Ever, What to do?

I've seen a lot of really funny intern stories on this page, and I'm bored and wanted to add to it. I'm having a horrible experience with one of my co-interns this summer and it's really weighing on me because he sits next to me 12 hours a day. Going to try to keep anon because I have seen analysts & associates scroll this page at their desk. 

To give some context, he's a freshman nepotism hire, and I think that's all you need to know. 

He unequivocally denies being a Nepo hire, and often brings up very strange topics to prove he isn't. For example, one time he turned to me and said "did you know that WACC is usually between 10 - 20 percent? On my interview I said 40% but still got the job!". Like wtf? 

Of course you got the job dude. 

He very consistently (and randomly) says stupid things like this at the desk. For example, he also said "I don't think our company has shareholders" (??????), telling an analyst "I think I'm becoming sort of an excel genius now, look I can do this" and does Alt WVG.

That's just the surface, he consistently says extremely immature stuff in the pit to both me and my associates. He has called me a dumb*ss in front of the team, and straight up said "r*tarded" to an analyst and 2 associates, one of them who looked at me with an open mouth. He's made horrible and unacceptable jokes too, regarding r*pe, etc.

He has also said done worse but for anonymity purpose I won't list it here. 

During a company social we were playing a card game that involved luck, and when he started winning (getting lucky), he decided to tell everyone at the table "this game is really easy, you just have to use your brain". Attending is 1 associate on our team, a few seniors in other groups, myself, and a NATIONAL LEADER who reports to CTO who was in that day. He then got too drunk and spilt beer over the table that we were playing the game on. 

He's also incapable of actually doing the job, always the last intern into the office, no etiquette, and doesn't understand the very basics. Some of the associates treat him like a make-a-wish kid, but at this point, I'm not sure if its because some they like him. The worst thing is, he doesn't think he's doing anything wrong. He's genuinely trying his hardest to fit in. 

An associate actually came up to me (an intern) to complain about him during a team social, talking about how he doesn't understand the job, is annoying, etc. What an interesting world we live in. 

The internship is almost over so there's nothing I can do about it, but it's been really weighing on me and not sure if I should talk to someone about his behavior. I'm looking to re-recruit obviously, but if I do come back full time, he would be here as an intern and I would feel really uncomfortable. What do you guys think?

Also wonder if he's going to get the return.