glen johnson used to be a real cutie who actually seemed to be scared of gettign punched. look at the the hopkins fight. then changed into a beasting, tank like machine. roberto duran against hagler was a rereshing surprise. duran knowing he could be engulfed by hagler. and also be out punched if so. kept it at a distance and really knuckled down his outside game. and did a damn good job against a more imposing fighter. nigel benn against eubank II was amazing. benn was a known bully and only followed the tear up fight plan. he to his credit started to turn sideways on a bit so he coudl use his left hand more effectivly and made his right hand less prominent so you could see it coming. he displayed his new style against eubank at old trafford and countered the counterpuncher almost outboxing chris at times.
nicky piper form standing aloof away from his opponant. became a body puncher and a inside fanatic. brought his downfall against benn and michalcsewski
from what i hear hector comacho was a very different fighter before he met edwin rosario. mike tyson to the technical eye, my friend said this and it made so much sense, especially comming from just a casual fight fan "i saw mike tyson on espn, that guy was incredable... he dident suck like how he does now" i little critical, but very accurate in the difference he is at the end of his career and from his beginning. the old mike tyson was conditioned, constantly throwing punches, constant head movement, power, incredable speed in hands, reliable body punching, great great great finisher. the tyson of his last fights was the old tyson for about one round and then a powerful loading up head hunter untill he gasses out reallying on his incredable chin which although is a formidable fighter, signifigantly different from his old self.
Nobody thinks Foreman changed his style. He was way more economical with his approach in his comeback.
As already stated Benn was a power puncher turned borderline cutie. Hagler turned from a (power punching) counter puncher in the 70s, to (by Roldan) little more than a face first brawler. Most dramatic maybe Tommy Hearns; who was a featherfisted runner as an amateur (something like 12 stoppages in a 155 amateur wins.)
dempsey somewhat changed his style electing to try to box more and stand straighter without the deep crouch and weave as much wich i believe worked for some opp. but didnt for others such as tunney,problobly due partly to his age ,inactivity as champion and the gruelling training he went threw in the days of old