When I worked for a large multinational energy services firm, one of the bosses I had (they changed every 2-3 years) was a huge bully. One of those "great coworker, bad manager" types. My wife had passed away, and as a result, my performance had dropped. One of his lines (verbal in person, not on paper) was "If you don't want to work here, there are plenty of people that do." He was the only boss I've ever had that m…
I scheduled a 1:1 with his boss. Half hour meeting, didn't tell my boss what we talked about beyond "a discussion about my career". My manager didn't even come up in the meeting.
Instant improvement in manager's behavior. Assholes know they're assholes, and the appearance of connectedness (along with deliberate efforts to keep them off kilter) is usually enough to keep them in line.