Demi Lovato is a diva and now the world knows it. The singer challenged James Corden to a Divas Riff-Off, and boy did she give him a run for his money. While James sang some older classics like Aretha Franklin's "Respect," Demi brought it back to this generation with Adele's "Rolling in the Deep" and her own hit "Heart Attack." The two proved to be very tough competitors but only one reigned supreme. Watch the video above and see for yourself.