Fact: you're going to lose a fight with a junkie hooked on amphetamine. There's a reason rehab cebters hire those huge security guys, pinning down sa guy like that is next to impoossible and usually rakes around 4 huge guys. Amphetamine screws up how you react to pain. You can punch him straight in the face and break his nose, and he will react by laughing. Just don't do it.

Secondly, people are not always what you see. A small story of a robbery:

A 16-year old kid(who was thin and scrawny, and looked even younger) walks into a convenience store and heads for the
register. When he gets there, he shows a paper to the cashier, saying "this is a robbery, give me your cash". This was i the middle of the day, with three other registers in use, and more than a dozen customers waiting in the lines. The cashier thinks "wtf", and ponders punching the kid. The kid shakes the paper once, and the cashier thinks "wtf" again, but hands him a 200 NOK bill(about 40USD). The kid once again shakes his paper, and this time the cashier gives him 500 NOK, thinking he must be satisfied now and that he'll piss off. But the kid is NOT satisfied, and instead produces a sabre he had hidden in his pants, and cuts down oveer the register, and the sabre gets stuck in the cashiers chair, right between his legs. The cashier faints.

If he had done a horizontal slash instead of a downwards chop, the cashier would be missing a head, the blade was razor sharp.

Don't confront a robber, either flee or comply. You have no idea what they could be capable of. Its better to lose your phone than lose your head.