I wouldn’t know! He used the sword a lot and was combining it with the axe in a same combo.
From what I understand, it’s all based around timing very small invulnerability frames as to not get interrupted while performing the combos? Anyway it’s crazy stuff, but I think he must have reached HR999 a long while ago, while I left the game at around 200!
One that doesn’t require much of any player skill is a “critical sharpness” sort of deal — I don’t recall the precise name —, that prevents any loss of sharpness on a critical hit. I have a Gunlance with 80% crit chance, and I had only to sharp it once or twice/monster, although it could go fast if not careful.
That sort of build works well with some of the good weapons that have very small sharpness zones too. I remember I was using it for one of my (many, collecting those is addiciting) horns, and for my insect glaive.