The true peak of Isaac. Repentance might just be this mod with more content, but the original incarnation is better. The Knife Pieces aren't so arduous to get (and there's a third one!), the Mausoleum has an entire back half to explore, there are a few interesting enemies which didn't return in Repentance, and the final boss is much cooler.
Not to mention that Mudeth's OST takes a fat shit over Ridiculon's. Well-deserved payback for throwing Danny Baranowsky out.