Spent the summer of 84 working in London Zoo and the elephant keeper told me the only thing you can do to hurt an elephant is to yank hard on its ears, the ears are relatively tender and this is sometimes enough to distract them if they get flighty.
Unfortunately they can also kill someone in a matter of seconds by rolling on them - and as one of the smartest species on the planet they are all too aware of this option.. Hundreds of workers in the Indian sub-continent have been crushed by angry elephants (and the Indian ones are know for being relatively gentle)....so heaven knows what getting on the wrong side of an African Elephant is like, fatal I guess.
He also told me that the reason elephants have a reputation for never forgetting is that when they judge a keeper and don't like them - they will never change their mind, even if reunited with said keeper 30 years later. Not sure if he was kidding me but he says when you go for an interview the elephant essentially decides if you get the job. No one really knows what makes them like or dislike someone...it's not like you can intimidate one....but if they don't like you - it's too risky to hire you and you end up sweeping up jackal poop instead.