I haven't played in a few weeks but I could certainly kill him if I wanted to? It's kind of a meme at this point that certain people find him undesirable and kill him every playthrough. You can have him not join your party on first meeting, you can attack him the night he comes to you, you can ask him to leave, and you can turn him in to the monster hunter at the very least. You can also just attack any of the companions unprompted... I'm pretty sure you can tell every companion to gtfo when they reveal their less desirable traits. I haven't personally removed anyone, but I got the option to tell everyone to leave at some point.
