Well here it is finally, the stream highlight of the Penance video!
The fight itself isn't actually all that hard but it's incredibly grindy and I made life harder for myself by giving up the grind halfway through the process.
The idea is that you're supposed to have 99,999HP and when you have HP like that, Auto-Regen will deal with any damage you take from his attacks. However I got sick of grinding and went in there with like 25,000ish health which made things a little difficult. But he went down in the end so it's all good! Don't forget to check out the stream for the X-2 playthrough!