Hard to know, really, since he started meeting quality opposition fairly late in his career. No shame in 0-2 against Liston, and 1-1 with Terrell and a draw with Machen along with some wins over fringe contenders indicates that he probably belonged to the top 5 more or less of the late 50's early 60's, but I would have wished to have more to go on. The one-sided loss to Ali doesn't tell us much, since he was shot (literally so, as is often added) by that time.
It seems that he was kind of an old time Davaryll Williamson, a contender with fearsome power, but fell short among fellow top fighters, although he did manage to beat a few also.
Lot of issues with this post, the least of which, the claim that Williams only made it to a number 4 rating which is untrue. He was ranked #2 when he was shot.
You know the effect those big black Powerful Heavyweights have on him. I wonder if Williams would be viewed differently if he was Swedish?
Cleveland Williams was plague by having a weak chin, being slow, having no real skills. He looked good against guys who wouldn't consider heavyweights by modern standards. Williams wasn't really anything special. I wouldn't even say he was a big puncher. He had a lot of knockouts. But who was he knocking out? He wasn't knocking out good fighters.
You don’t have to have knocked out world class fighters to go down as a big puncher. Is Wilder not a big puncher? What great fighters has he knocked out? Liston and Foreman both said Williams hit like a truck, that says more about his power than a boxrec list.
Don't care much for the "Big cat" but he could whack everyone he fought says so. He looked pretty quick to me on film but apart from that he is nothing amazing.