Betulio Gonzalez, especially in his third reign. Used it to knock out Martin Vargas and Shoji Oguma (the latter in fan-yourself-hot conditions) late, and came on strong in the last five rounds against Espadas and against Oguma in the draw. Technique and power held, and workrate actually improved. In both of the knockout wins he looked like he was consciously pacing himself. This wouldn't have worked without his chin, though, because in both cases "pacing himself" meant eating a lot of punches.
Charles wasn't showing Power, technique or workrate in round 15 against Marciano, he was showing a desire to survive at the very least
Plenty of good ones named so far. I'll throw McCallum, Whitaker, Jofre, Ross, SRR at 147, Gavilan, Griffith, Canto, Basilio, Jones, and Pedroza into the pot to keep things rolling.
Hopkins and Duran come to mind. Major recency bias but Donaire looked great coming back to 118, lower level to ATGs but just a thought!
Only a little bit, I'm new to this whole "boxing" thing Pretty sure he had a good 3 fight series with Zale