Cory Spinks did it twice. After losing rematch to Zab Judah, He moved up and won IBF Super Welterweight title from Roman Karmazin. Couple years later He lost that belt to Verno Phillips, but He won it right back after Verno vacated. It's probably more rare for fighter to win a title after losing in non-title match.. Don't some organizations even have it in their rules now, that You have to be coming off a win to fight for a title?
Muhammad Rachman lost four fights in a row with one being a KO loss and the other being a six round decision loss to win the WBA belt via KO.
Not counting guys who dropped their titles then won them back in rematches: Foreman's second incarnation he lost to Tommy M right before the Moorer fight?
The devil is in the detail with this one. The first fight between Charles and Walcott was pretty conclusive, and Charles should probably have sat on the result. The second fight was a wee bit controversial, but Charles could probably have toughed it out. The third time he pushed his luck too far. Bottom line, when you see an unusual fight pattern like that, it normally happened for a reason.