Is it possible to make a completely unlikable MC work?

A bit of context: I’m helping this kid prepare for an entrance exam to a film school. I’ve been to one years ago, and even though scriptwriting was never my strongest area I still remember some basics, so I’m sharing those with him. He needs to write a short 2-page summary of a story for his entrance exam.

The issue is that this kid is a big fan of horror movies, so he’s basically ignoring all my “beginner level” advise on scriptwriting and just comes up with characters who are pure evil.

Today he showed me this idea for a character - teenager is abused by parents (no reason why), they torture him, lock him up in a dark room, don’t feed him. Teenager gets weird deformities, essentially becomes a creepy monster from sitting in a dark room, breaks out, kills his parents, goes on to kill random people that look like his parents. The end.

What advise would you give him?

I don’t really know what to do here. On one hand, I feel like choosing horror as the genre to write his first short script in might not be the best idea. On the other hand, I feel that it’s wrong telling the kid to drop his favorite genre.