The worst example I saw (and paid money to see, I might add) was at a concert of the band Widowmaker back in the mid 70's.
Lead guitarist (Ariel Bender a.k.a. Luther Grosvenor) and Bob Daisley were having a right ding dong, which ended in one spitting in the face of the other.
High on drugs, part of the act, who knows? It was awful.
I remember that, but not very much of Bob Daisley's bass playing.