It's a tie between Vance, Chrys, Shanx. Flair, Dezra, Syndra, Treasure, Zane, Iris, and Amelia, who have all been featured as children, teens, adults, and elders. The most radical changes are usually between their prepubescence and their teen years, but that isn't always the case.

It usually depends on what happens canonically to cause those changes, though.