Loma Rigo Floyd JMM GGG brook Canelo khan My reason is as an opponent, Rigo is the higher pound per pound fighter at the time, maybe JMM has a claim, I can't remember, but I penalise Floyd a little for not honouring the catch weight. I listed best to worst win.
Worst to best Khan-Canelo was meaningless so I’m putting this worst Brook-GGG and Loma-Rigo I’m putting at a tie because both brook and Rigo jumped up two weight classes where they really had no chance at all winning. JMM-Floyd is actually the best because JMM was rated p4p number 2 at the time but JMM ended up not only getting robbed by Manny at the same catchweight which indeed prompted a 4th fight in which he knocked Manny tf out. This actually makes this the best.
Okay you do make a point but as much as I hate Khan, that KO potentially ensured he will have brain problems later in life.
In order of fail, and also least meaningful win: 1. Rigo against Loma. You'd think it would be a win win for Rigo, but that was disgraceful, he trashed his whole career with that quit job. 2. Khan against Canelo. Brought his track shoes but oops didn't bring the boxing brain and chin you need to hang with Canelo. This was never going to work. 3. Marquez against Mayweather. Commendable effort, deserved the fight, but as great as Marquez was he was never going to have luck countering the faster, longer, greater Mayweather. 4. Brook against Golovkin. Well Brook outboxed and exposed GGG's weaknesses for a couple rounds, only to fade quickly as GGG's strength and power took over. This one unlike the others was completely about size, it surely would've been different if Brook was a true middleweight. Brook deserves big props, but is respect and a decent payday worth it when you're physically damaged and your career is shortened? Moving up two classes really shows how much we have to admire the old school guys like Armstrong who beat truly bigger men, they were really risking it.
Which coming up fighter has better chance to win. From less to better chance; Khan, ko waiting to happen. Brook, ko waiting to happen. Marquez, UD loss waiting to happen. Rigo, i think its ko loss waiting to happen but some nut case here claim he has a chance and now refuse to give Loma his props.
Also in order of fail/least meaningful win, as I'm guessing is the case with the OP. Canelo-King Amir Loma-Rigo Floyd-JMM GGG-Brookzzzzzz -Khan was the worst, because he can't really fight. A naturally bigger guy with good fundamentals, reading comp and a solid punch was always going to have him figured out after a couple sessions and KO'd before the late rounds. -Rigo hadn't done a darn thing worth writing home about in four years. The nicest thing you can say is that he got rounds in during 2014 and 2015. You can't say that for 2016 and 2017, because he'd boxed all of nine minutes in that twenty-four month spell, and six of those were spent sharing a ring with a guy who has gone life and death with Josh Wale. That sounds like one half of the most talent ever seen in one boxing ring. Except Miguel Marriaga (good fighter, also past his optimum fighting weight at 130) and Jason 'I Went To War With Swifty Smith' Sosa did more to merit praise in their fights with Lomachenko than Rigo did. In summary, an old, inactive super bantam who didn't even feel like putting it all on the line with his painfully thin career hanging in the balance. No thanks. -This wasn't the aptly prepared welterweight version of JMM we saw later on, but Juan never showed the slightest inclination to surrender despite being clearly outstyled. He at least went on to achieve feats of significance at the weight. -Brook was skilled, prime, came to win, had four very competitive rounds before Golovkin's will and physicality shut the resistance down. Juan is by far the most valuable name of any of these opponents, but I give the edge to Golovkin-Brook, on account of the evident competitive fire in Brook's guts and his ability to compete for more or less as long as he was in there. We have pretty much the same list, save for a sliver of difference between Loma-Rigo and Canelo-Khan.