What fighters, in your view, would become 'unbeatable' if only they had a certain attribute. Why? For example, if Jorge Linares had an adamantium chin, he would be extremely hard to box with, as his timing, movement and speed was impeccable. Kuniaki Shibata: adamantium chin. Unless your name was Ernesto Marcel, you were not keeping up with this guy and would be unable to box with him, especially when he has momentum. An iron chin would allow him to take on the bangers in a more confident and ultimately dominant way. Johnny Tapia: Power. Tapia was a monster anyway, imagine him with power. He would be absolutely destroying people, and be a truly complete fighter. Any others?
For a fighter to be "unbeatable", I think we'd need to consider styles; a boxer-puncher always seems to match up the best. Maybe I'm reading into this too much. Patterson/Wlad/Lewis - Iron chin Chavez - Elite Speed Tyson - Stamina Olivares/Rose/Jofre - making weight. Harada's BW skill at Fly. Foster - Saad's chin Armstrong - Devastating Power Lomachenko - More Dog* *As in a bit dirtier, more rough and unforgiving to body shots/foul play ect. He wouldn't be unbeatable, and it's not one attribute, but it is close to my heart. If you gave Saad's chin, and Greb's stamina to Marvin Johnson, you're looking at an unrivaled animalistic swarmer at 175lbs.
Obviously the correct answer is giving Joey Maxim's chin to Roy Jones Jr, but that's a little unfair.
Guys like Fighting Harada, Jeff Fenech, Johnny Tapia, and Jung Koo Chang would have been absolute wrecking machines if they were gifted with KO power. Can you imagine??
Tyson Fury - Deontay Wilders Power Floyd Mayweather Jr - Thomas Hearns' power George Foreman - Joe Frazier's stamina Willie Pep - Sandy Saddler's power Kid Gavilan - Ray Robinson's power Riddick Bowe - Evander Holyfield's work ethic Sonny Liston - Muhammad Ali's speed Every Fighter Ever - Primo Carnera's "connections"
To me I think if you combined the attributes of Thomas Hearns (height, reach, power, jab, speed, outside boxing ability) and James Toney (iron chin, counterpunching, combinations, in-fighting skills, defense) you would get one hell of an "undestructible" force of nature.
I love the idea of making a perfect fighter from guys who already existed. There's loads too. Just a few I've come up with: Taking José Napoles' skills, style and smoothness, then adding RJJ-esque explosiveness and LaMotta mandible. Mix up the fab 4! Hagler's style and physical attributes, Hearns' dimensions, Leonard's Ring IQ, footwork and speed with Durán's "craft". If Miguel Canto was blessed with the power of Pacquiao and the chin of Villa, and the presence of mind to use his right hand more, you're looking at the best fighter in history imo.
Call me crazy, but even the punching ability of Herbie Hide on a prime Ali would be awesome. None of the Frazier fights would be close. Tyson with stamina is another pick, but even such a version could be outboxed. Thats the same problem with a "iron chinned Lewis" or "quicker Foreman with gas". The best, quickest moving and good durability jabbers have the best style to even beat a high stamina puncher. Of course a fight likes could have some scary moments due to the power, or the power leading to winning more rounds. But imho there is a reason the style of Holmes and Ali was extremely successful.
Jose Napoles - tougher skin. And give him title shots at 135 and 140 in his prime and he'd be as damn near perfect as you could get.