1. Stop his heart beat - Disrupt his organs, such as bleeding - somehow ends the blood flow to his heart - etc etc 2. Numerous accidents: - car crashes - Heavy object falls on him - occupational accidents - falls, trips - electrocution - medical accidents such as wrong use of needles or wrong injection - allergies, infection 3. Torture: - chinese water torture - Lets not go into deatils 4. Weapons: - guns, missiles - atom bombs etc 5. Murder: - Stabbing - Shooting - Sniper etc - Deliberate food poisoning - Bashing - hit man etc etc