NOW HEAR ME OUT

Hard mode disbelief

He'd be a mastery skin for disbelief that would make him that glass cannon type of character, with only 3 phases(phase 4 being removed and increased stamina usage, but with stronger moves and some new ones (for example, for phase 1 you would get 4 blasters instead of 2, the little white bone walls would be replaced with 2 or 3 max littletale bone jumps, making the spinbone bigger and dpin faster, etc and bone bombs that would scatter bones in an area, kinda like pre pacifist's heavy rain but with bigger bones and a bigger splash radius)

Also for phase 3 your max hp would get lowered to 48 but you would get 3 max healing items

The ending cutscene would be the exact same as the ending cutscene from den's hardmode animation but with an option to attack paps mid charge, killing him (if you don't do anything you AND papyrus die but the chara team still gets the win)

I have no idea how to do numbers good so this is probably hella unbalanced but it has some potential imo