Scythe, oh scythe...

[shadow milhouse]

How the hell do you even use this thing? It would be horrible on arbarghus, since you just fly off the platform into the acid, and even then it just sorta rockets you into enemies if you miss one of them. Such fail, many unwanted deaths.

[swightly]

I guess this weapon is more geared towards speedrunners by utilizing the air dash spam to avoid obstacles and zip through horizontal tower parts quicker.

You don't really want to melee bosses with this weapon however since I don't think you get invincbility frames while dashing into their hitbox. There's always other amazing projectile weapons for making Arbarghus pretty trivial like the boomerang and ha-hadouken. I'd probably lean more towards the boomerang because it's an amazing crutch weapon in most situations.

[MasterLuigi452]

Flamethrower is a great ranged weapon for bosses as well.
Not so much on Arbarghus, but still a nice ranged wep.