From Divinity Engine Wiki
- call LeaveCombat([in](GUIDSTRING)_Target)
Makes _Target leave the combat it's currently involved it. Should not be called if _Target is currently not in combat.
- Unless you first teleported _Target away to a safe location, it's quite likely that it will rejoin the same combat during the next frame. If you wish to prevent it from rejoining any further combat, call SetCanJoinCombat instead (but be careful to restore it again later in case this is done for a player).