Is Gonzalez really an example? 3division champion in his 47th fight before he loses a close fight that most thought he won. I think he aged and went up divisions rather than rise and suddenly crash.
Chocolatito's time on top in reality lasted years longer than just when casuals started to know about him. Unless by "on top" you mean the fame & riches, but...fuck all that worthless crap. That isn't what matters.
Jeff Lacy. The unstoppable monster. Never really had convincing performance after Calzaghe took his soul.
Naseem Hamed Reached the top, lost his discipline and focus, lost his first fight...then crashed and blew up like a beach balloon. Odlanier Solis Stepped up against Vitali in a fight alot of people thought he would win. Folds like a deck of cards. Then crashes to Tony Thompson in a comeback and retires.
Leon Spinks. After the Ali win and loss, he was convincingly TKod by Gerrie Coetzee. He never really recovered imo.
David Reid. Won Olympic Gold and then a belt at 154 early in his career. Got crushed by Tito and it was all downhill after that with eye problems and trouble making weight.