Something that adds a great deal of variety to almost any hard dungeon run is the random boss. That powerful unknown factor that you are going to have to deal with to claim victory. So I'm wondering: What random boss do you fear the most? Which one has caused you the most pain, destroying your seemingly assured victories?
Has the goo blob been showing up everytime you shoot for warmonger?
Has bleaty been making you wish cydstepp was an assured dungeon drop?
Who has been giving you the most trouble?
For me it is always Super Meat Man. My regen fighting is a big weakness, and this giant annoying blob of health can bring me to tears when he wants to.