My surprise seeing the Lamb in the void. For some reason I thought only "regular" bosses could appear.
Also for some reason Delirium kept random dropping unavoidable bombs that would instantly explode and do damage. That was fun. I was basically on a time limit, since these bombs constantly hit me, and I had to manage to kill him in between Polaroid procs.
Beat it as ??? on a loop. That was a productive loop. Satan, Lamb, Boss Rush, Hush and Delirium all on the same run. I thought there was an achievement for beating a loop? But I didn't get it. Oh well. Edit: Looks like I need to beat the Lamb on the second loop. I'll keep that in mind
That was also my first Delirium kill. With the right items, ??? isn't really that hard. Little CHAD + Dark Bum is a slam dunk.
The wiki says this
Achievements cannot be unlocked during a victory lap.
That's not true. I unlocked the Hush, Boss Rush and Delirium achievements just fine with ??? in a victory lap
Donation Machines no longer appear.
Isn't true either. In fact I had an entire secret room full of coins and a Donation machine in a victory lap
A rerun doesn't allow achievements. A victory lap seems to work just fine with them.