Lady GaGa - Dance In the Dark, Monster
Rihanna - Russian Roulette, Cold Case Love, Fire Bomb. I also think Rehab was kinda a sad dark break-up song
Katy Perry - E.T.
Avril Lavigne - Take Me Away, Together, My Happy Ending, Nobody's Home, Forgotten, Slipped Away. Under my Skin was full of darker material from Avril
Ashlee Simpson - Catch Me When I Fall, Eyes Wide Open