Check out this video from Rich the Fight Historian: Ali vs. Alvin "Blue" Lewis, 1972. Hell of a fight. This is the first time I've seen it. Lewis was a tuff mfer. This content is protected
Ali was not a particularly heavy puncher, no. His power is certainly below average of the better heavyweights.
Not a one punch banger but no powder puff puncher either. Muhammad could hit hard enough,though,when he put his whole weight behind his shots. His strength in that area was volume and speed of punch. "That was n't the guy I was supposed to fight. That guy could hit" Sonny Liston 1964.
He knocked out guys with iron chins. He didn’t knock out some guys with chins on the softer side. He was bang on average I’d say - he had the potential like any HW with a well placed shot.
I wouldn’t say he was below average, he could hit when he wanted to. He wasn’t a monster knockout artist but if could finish an opponent if he needed. I think he was the first to stop Liston, foreman, and bonavena which would be very hard without at least some power.
Ali had to contend with bad hands at different times during his career - even causing him to cease heavy bag work for some period prior to certain fights. Notably, before fighting Foreman, Ali confirmed that his hands were in good shape, no issues. IMO, Ali was hitting Foreman particularly hard throughout their fight - perhaps the power in Ali’s shots wasn’t as noticeable due to Foreman’s solid chin - a chin that wasn’t fully appreciated as at that time - but certainly, Ali was the first to crack that chin and the only man ever to put George down for the 10 count.
Anytime he fought a feared puncher (Liston, Foreman, Lyle, Williams, etc) he not only won, but, won by knockout. He also stopped guys like Bonevena and Frazier that were hard to stop. I think he went easy on a lot of guys. But, he could punch when he needed to.