Patch: Tespia 1.2.190

I don't think HHs reduction is affected by resistances...it's 99,999 every time, isn't it?

You'd want that wouldn't you? =P

If the monster has 100k HP or less, the monster's HP is reduced to 1. This is the case where elements don't really matter.

Otherwise, it's suspected to do the stated damage amount in the skill description. Testing this on a boss monster with just over 100k HP gives you a nice clarity picture. (you could do it on CGs, but then there's a human discrepancy issue because the HP bar is so small)

About the only really amazing thing about HH is that there's pretty much nothing that can escape its damage. It doesn't miss (lol GPQ golems) and it doesn't seem to be affected by super wDef (killing Tae Roon pretty much proves this last time I checked). Exceptions are monsters that are meant to be hurt only by the default attack, such as the Halloween Ghosts.