Anon La Ply

Sometimes the small ego's create problems too.

The most problematic band member I've encountered was a bass player who couldn't play that great, hit wrong notes, forgot parts, wouldn't practice and he was a massively outspoken control freak. He was very insecure in his playing and himself and I was his biggest enemy for some reason. I quit after about a year.
That is actually a big ego reacting to being incapable of feeding itself with big achievements, hence the control freak angle (a sign of extreme insecurity). I played with a bassist who was like that and she knew she was in the band because she owned the rehearsal space

Ego is a defence - the wall that protects what you think of as "you" from what is outside of you. You more insecure you are, the higher the wall, and the less responsive you are to outside influence - especially band mates :)