Ali was not only a fine athlete - he was both highly intelligent and well spoken. He showed a great deal of moral courage in standing up for what he believed - even going to jail for it.
I'm forgetting the opponent now... but it was a championship fight - where Ali threw an uppercut that lifted his opponent off the floor. That flurry of punches... 12 punches in 2.8 seconds.
Ali is the greatest heavyweight fighter ever, his second fight with Joe Frazier was referred to as The Thrilla In Manila is maybe the best heavyweight fight ever, but had negative long term effects on his health. Definitely react to Mike Tyson who is the most intimidating fighter.