Benitez vs Napoles depends on the weightclass,I'd place my pick on Napoles if they're fighting from 140 to 147,not for super welterweight tho.
Maybe Roldan,as the more talented and vast skilled guy.
Kalambay in a competitive fight.
Chris John outboxes Manuel Medina Joe Louis outslugs Earnie Shavers Hot take for both of these, but the second is a bit of like "who lands...
I'll try to gamble my chances on Chacon,as he was a bit more proven.
Frazier,if you beat the nearest version of peak Ali,your name shall be remembered in heavyweight history.
He doesn't care, who,where and when he's gonna fight, he's only worried if he's going to fight or not.
I think Jung Koo Chang might be self taught too,never did much of boxing until he hit the gym,while also had no amateur experience at all. Yet...
Mostly their physique comes first,then skills.
Greg Haugen has that answer,or maybe even Muhammad Rachman,though both weren't too short or skinny.
Bump
So far..I can only name 3 who just made their own style,crafted and carved the techniques and used em in their own tactics too. Manuel Medina Jack...
Fights where you felt bad the most for the underdog. For me though,i'd say Hiroyuki Sakamoto vs Takanori Hatakeyama obviously,watch that fight...
I think Greg Haugen is great to learn from,I know he still has some kind of muscles,but he's still pretty small and skinny.
These type of fights mostly ends by KO for the underdog,though..they did beat up the favorite to the punch before.