David Frith wrote that McKenzie's "sturdy shoulders drove the ball with a smack into the pitch, and the lift off it was often too much for even the best batsmen in the world. Boycott's was just one forearm broken by his bowling." McKenzie also put West Indian keeper Hendriks in hospital requiring brain surgery.That impression of McKenzie is almost certainly due to his very leisurely looking run and action. Though of nowhere near the same pace (I'm rubbish) I've encountered a few similarly deceptive bowlers.
Not sure one incident is a good indicator. Brendon Julian once broke Sanath Jayasuriya's arm.
But by all accounts he was a mild-mannered character who didn't like hitting batsmen.
Trevor Bailey estimated that the difference in speed between Tyson and Statham was similar to that between Statham and himself, which he said was considerable.