You can describe someone as a prodigal son or daughter if they leave their family or friends, often after a period of behaving badly, and then return at a later time as a better person.
"distributed gifts with a lavish hand""the critics were lavish in their praise""a munificent gift""his father gave him a half-dollar and his mother a quarter and he thought them munificent""prodigal praise""unsparing generosity""his unstinted devotion""called for unstinting aid to Britain"