Marciano comes to mind. He had to work extremely hard to get where he was- probably harder that anyone.
Marciano had unreal power, which is a natural ability. In reality, ALL of the all time greats are extremely talented. Hardwork with a lack ability can get you to be a good fighter, but all of the true all time greats had immense talent in same way or another. Obviously, some more talented than others. Hardwork ALONE will not get you there.
Marciano had incredible power, weird squirmy elasticity, was very strong and had supreme stamina. He had an abundance of natural ability, I would say.
Add to that a great chin. Power, physical strength, chin, and stamina are all God-given talents. Marciano did not lack ability. Dude is acting like Rocky was Mikey Ward or something.
The OP says he thinks Rocky had to work harder than anyone to get to where he was. He doesn't once say he's Mikey Ward.
Would George Foreman be considered one lacking in natural talent? He had great power, but his ability needed much work to get to where he was.
Pazienza couldn't even tag him clean! And that was Pazienza who beat Duran, the same Duran who beat Sugar Ray Leonard! So if guys of Sugar Ray's calibre can go a full round without punching Jones he must have loads of talent! I mean some call Sugar Ray Robinson the best of all time but it didn't help him against Jones at all.
I think this question is easier to answer if you ask for which ATG dedication and discipline was most important to success. If you look at the excuses made for Tyson, you'd think he'd be the answer here. Going from unbeatable to one of Buster Douglas' punching bags. But I think Frazier, for example, is a better answer. He really needed to be fully motivated and dedicated to be a force, I'd say. Probably Marciano to a degree as well. Not that these guys lacked talent (of course not), but just thinking how well they'd do (or rather, wouldn't do) if they slacked in training. Armstrong probably fits this bill, as well. But, of course, on the other hand, who did do well with lacking dedication? Well, Ali throughout the 70's, I'd say. But otherwise, most gets found out pretty quickly when they drop in dedication. No matter how skilled. So perhaps my way of posing the question didn't really add much - except a dig at Tyson fans and some adulation of Ali. Well, I can live with that.
George was an Olympic champ if I recall, I think he had talent in spades. I don't think anyone can be an ATG without having natural ability. Even someone like Walcott or Moore who endured many losses prior to a title shot, they showed they had talent.
Yes, I forgot about the Olympic gold. Maybe he had to smoothen out the rough spots, which isn't exactly lacking in natural ability. This is a tough question. Who was the guy that beat Byron Mitchell for the 168 lbs. strap before Mitchell lost to Calzaghe? It was a rematch of their draw a few months earlier.
Jim Watt. He did not do anything particularly well but was very fit, could do the 15 rounds, was intelligent and kept it all very simple ...and very effective. Nothing God given beyond health and fitness.
A natural asset George had was his instinctive radar. It meant he could walk up and land any lead punch without first setting himself from a walking position. Lead uppercut at range and know it would land without looking. You can't learn that. Strength can be developed but George obviously had a high natural strength too.