L.A. Reid is a hit maker. He is responsible for a lot of huge careers – the names Pink, Justin Bieber, Rihanna come to mind. That's why he is an 'X Factor' judge. However, he has one massive regret in his career and that is letting Lady Gaga go. That's right. Reid had signed her when he was the head honcho at Island Def Jam and then swiftly dropped her.