Well, there are many possible wats. You could shoot him multiple times with most and type of gun, bow, or crossbow. You could stab them to death with any number of things, best one is a knife. (not a butter knife or a plastic knife) You could suffocate him by simply removing him from the water. You could starve him by eliinating his food source wherever he might reside. Or, you could just leave him alone like a normal person. Your choice. xP