Other forms: last laughs
To succeed at something after being doubted or scorned is to have the last laugh. After a humiliating loss in the first game of the World Series, your favorite baseball team had the last laugh when they swept the next four games and won the series.
Having the last laugh is a kind of vindication — you have to go through some unpleasantness first, often being ridiculed or considered a failure, before ultimately triumphing. Many movie plots rely on the satisfaction of a character getting the last laugh, like a scientist whose belief in aliens is mocked until the day a UFO lands in her home town, or an unpopular kid at school who has the last laugh after being voted class president.