Any spring to mind? One that immediately comes to is Barrera after the Morales fight, he really tightened his style as he got older, damned near beating a Peak JMM in the process. It’s also the anniversary of Barrera morales 1.
Joe Parker is becoming more aggressive under Andy Lee. He had regressed or stagnated when being trained by Barry. The results are starting to show.
Danny Lopez. In January 75 he'd just lost 3 in 4, two by stoppage. And then he went on an absolute tear and cemented himself a FW legend. Another one is Wlad Klitschko, when he lost to Brewster he was seen as a joke at HW. A parody of the stiff EE style of fighting that just couldn't compete at the highest level. He then went on to establish himself a HW legend. Those two are standouts for me. But if you consider the pre "obsessed with an unbeaten record" era you'll see loads that look amazing on paper, even though at the time it wasn't that big of a shock that someone who lost went on to have success.
After Tyson Fury's career began to stagnate, with run-of-the-mill title defences against also-rans Dillian Whyte and Dereck Chisora, and fans were beginning to bemoan his lacklustre heavyweight reign, he achieved an heroic comeback with a hard-fought points win over MMA giant Francis Ngannou.
That Irish guy who beat Chris Eubank twice and Nigel Benn despite being pretty mediocre at 160. Forgot his name.
In Freddie Pendleton's first 35 fights he was 17-15-3. He then went on to beat more than a handful of good fighters and win a world championship.