Just in case you didn't know, James Corden is really good singer! You probably know that simply from the extremely successful "Carpool Karaoke." There's a good chance every single person in America has seen "Carpool Karaoke" at least once.
He uses his singing ability for a number of bits on his show including "Riff-off" where he, basically, challenges his guests to a singing competition. This time he took on Demi Lovato and, well as you might imagine, she out shined him!