Dr. Tyme!!! Dr. Tyme, they plucked out a minor Doom Patrol villain (he only officially fought them once) and did such a great, fun job with him. Not to mention that they actually successfully managed to adapt one of, if not the, weirdest, most high concept supervillain masks in comics.
As is par with the show, all the characters get to shine, especially Caulder, Negative Man, and Cyborg. Timothy Dalton delivers a nuanced award-level performance as we look at the reasons behind Caulder's actions. Negative Man's plotline is a poignantly tragic affair.