Make a team of 6 characters, all the same class. How deep can you go? My 6 berzerkers got to 50 before I got bored and pulled them out.
Part of me thinks that 6 clerics would be the best. Two hasters and One healer. Self haste to start, then haste the healer to high heaven. Kill enemy ever so slowly. There’d be a LOT of animation canceling, or it’d never work. And you’d use lots of food. But part of me is just crazy enough to try!