I can't get rid of this Undead Warrior!

Hint 1 of 4:

Attack the poor thing!

Hint 2 of 4:

Whiff, whiff.  Hmm ... perhaps you need something a little more potent
against this Unholy thing?

Hint 3 of 4:

Something like the Vial of Holy Water?

Hint 4 of 4:

THROW THE VIAL AT THE UNDEAD WARRIOR.