Behind the Bastards is my top recommendation. Just learning how truly awful the world has been for a few thousand years is soul crushingly entertaining.
I love how they combine it all with light banter. Without the banter, most of the episode would be unlistenable, as you would be too depressed and tie yourself on a train track.
I also love that Robert brings on repeat guests for certain topics. If an episode has lots of dead babies, it gets one person, Nazis often get Matt Lieb with his new sound board.
My favorite episode of all time is Action Park, with Garrison as host and Robert as the “guest”.