Arthur was never a fan of unnecessary cruelty. Even when fighting enemies or people he loathed, he would never inflict more pain than he believed the other person deserved. He liked to call it justice, but he wasn't delusional.
Justice was what the victor decided.
If the vampires here defeated him, they would be justice. He would be the intruder who attempted to exterminate their race. And the act of defeating him would be glorious, fulfilling, and, as they would believe, an act of justice.
The bodies slammed to the ground, their insides emerging into the world in an unsightly fashion. Arthur remained in his spot, having executed at least a hundred vampires in a single strike.
Vengeance was not without cost, either. The ability to choose several targets to suffer his wrath came at the dear cost of his sanity.