Mike McCallum. Ended his career with a trilogy with Toney. While he didn't perform as good as he did in the other two; he still put up a decent performance to then go & settle off into the sunset.
Vitali Klitschko had a pretty satisfying end to his career. After first retiring as the reigning WBC champion because of injuries in 2004, he came out of retirement four years later and in his first fight back challenged Samuel Peter for his old WBC title. Peter who was then 30-1, had only lost to Wlad previously in a exciting fight where he came close to stopping Wlad before losing a hard fought decision and many thought that it was a big risk for Vitali to face Peter in his first fight after four years out. Vitali surprised a lot of people by totally dominating Peter and become the first man to stop him. After that, with Wlad holding the other three major heavyweight titles, Vitali made nine further successful defences of his WBC title before finally retiring for good in 2012 at the grand old age of 41. So not a bad way at all to finish a career.
It needs to be said that he wanted an immediate rematch but Leonard went into retirement and tried to offer the rematch way too late, after Hagler had already retired.
Max Schmeling invested his money, bought the only coca cola bottling plant in post war Germany and made millions. Enough to toss Joe Louis some cash when ever he needed it. That's a perfect retirement.
Marciano, Mayweather, Lewis (though I too wish there was a Vitality rematch). How about Daniel Zaragoza? Beats undefeated much younger Wayne McCulllough then loses his WBC title in an entertaining fight to future hall of famer Erik Morales, then walks away.
Classic has some strange obsession with this thing like Thor in Avengers: Infinity Gauntlet — “He hasn’t beat me twice.” They fought. Lennox won, fair and square. Punched holes in the guy’s face. See, what Lennox needed was a brother — Chris Byrd beats you up, go run to your brother and ask him to avenge you; Corrie Sanders knocks you out, run to your brother and beg him to beat the guy. Ross Purity whips your ass, go tell mama to ask your brother to do something a about it. Lennox beat the guy and retired on top. With him out of the way the brothers had a chance to rule over a weak division. I bet they still send him Christmas cards thanking him for vacating so they could have their time.
