Demi

Demi Lovato charmed America as a teen TV star, earning generations of self-styled Lovatics, partly because she wears her heart on her sleeve, as displayed on "Heart Attack." With gut-wrenching vocals filled with passion and power, Lovato describes the vulnerability you feel when you truly like someone: "Pain is more trouble than love is worth / I gasp for air / It feels so good / but you know it hurts."