I've been very lucky. Played in three different progs for 100+ seasons total, had four different commishes in those progs, and they were all terrific:
habsfan1
contrarian23
oram13
coachgreat1
If you ever see any of these guys advertising for new owners, rest assured you can join their leagues knowing they'll be properly run.
Whatever knowledge I have of bad commishes is second-hand, so I won't comment. But some of the stories are pretty hilarious. I hope to read a few more in this thread...