I couldn't find any threads on this... maybe I'm blind though

Anyways, I'm looking for a good extreme challenge to try on my next play-through

I already have a NLBLLG (No License Board Low Level Game) going, I'm up to Giruvegan events with it, but kinda want to put that aside for another challenge any suggestions?

I'm fine with trying anything and everything, so give me your opinions on the most difficult challenges