There's No such a thing as a Perfect Fighter, every past Great had their kryptonite. If you asked me who I think the greatest and most accomplished HW, I'd say Ali. But if you asked that who my H2H #1 is, I can't answer that. H2H rankings don't make sense for the afromentioned reason.
I agree that there is no such thing as a perfect fighter. Which is why it annoys me when people deify Ali as an unbeatable force. He's just a man.
He also had his way with Sonny Liston, who's a lot closer to Fraizer level than Mildenberg(and had similar offensive weapons). For The same reason Cunningham gave Fury hell but Wlad couldn't touch him, the same reason Mavrovich performed better against Lewis than Tyson, Golota, Ruddock, Briggs, Grant did. Some fighters just have off nights, sometimes they fight down to Level of their opponents. His toughest opponents truly define a fighter's quality.
On the I think even tinman would agree that there's No comprasion between the greatness of Ali and that of Pac.