Put the phone on top of all the the atomic bombs in the world, gathered in one pace, and detonate them. Just stand like 200 feet away to watch the bomb explosion show. End of the phone.
Try jailbreak it and pull out the USB chord, or hold down power button on phone, that will cause some issues
That was a bump but ok OT: you could just update iOS until it eventually tries to kill itself because of Apple's stupid de-optimization program (so you are forced to buy a new phone).
Does anyone read the title ffs? WITHOUT PHYSICAL FORCE. Anyhoo, overvolt it, unplug phone during jailbreak, put it in water, microwave, set it on fire and etc I'd like to see you send it a boat load of electricity.