also added kill-once objectives

code/game/gamemodes/objective.dm

@@ -173,6 +173,30 @@ GLOBAL_LIST_EMPTY(objectives)
 /datum/objective/assassinate/admin_edit(mob/admin)
 	admin_simple_target_pick(admin)
 
+/datum/objective/assassinate/once
+	name = "kill once"
+	var/won = FALSE
+
+/datum/objective/assassinate/once/update_explanation_text()
+	..()
+	if(target && target.current)
+		explanation_text = "Kill [target.name], the [!target_role_type ? target.assigned_role : target.special_role]. You only need to kill [target.p_them()] once; if they come back, you've still succeeded."
+	else
+		explanation_text = "Free Objective"
+
+/datum/objective/assassinate/once/find_target_by_role()
+	. = ..()
+	if(.)
+		START_PROCESSING(SSprocessing,src)
+
+/datum/objective/assassinate/once/check_completion()
+	return won || ..()
+
+/datum/objective/assassinate/once/process()
+	won = check_completion()
+	if(won)
+		STOP_PROCESSING(SSprocessing,src)
+
 /datum/objective/assassinate/internal
 	var/stolen = 0 		//Have we already eliminated this target?