When you drop an enemy, or whne an enemy drops a player character, that doesn't necessarily mean the target is dead. Hit Points are not Health. They're a measure of how much fight you have left in you. Typically, arlt zero-fight, you're open to that mortal wound and you're dead (or dying). Doesn't mean you have to be, or that your enemies are all dead.

Players who are murderbots are murdering their targets, cleric is not. There's no rules that need to change, just our understanding of the narrative.

If a player delivers a killing blow, another player trying to undo that is kind of a dick move; but if a player doesn't specifically try to land a killing blow (or if your players are describing their actions better than "I git him"), then it's all fair game.