Some hit it out of the park, and others not so much!

All of Hollywood's hottest celebs attended the Billboard Music Awards in Las Vegas on Sunday, and they turned the red carpet into their own runway to showcase their designer ensembles. Jennifer Lopez looked gorgeous as usual, but we find her white cutout dress a little too ice skater chic for our taste. Mariah Carey showed a lot of cleavage in a black dress, but her frock wasn't all that flattering for her legs. Harry Styles, meanwhile, just looked plain hot!

Rita Ora dared to bare with a thigh high slit dress, while host Chrissy Tiegan proved why she gets paid to be pretty in a low cut sequined jumpsuit. Zendaya is our best dressed of the evening, in a funky patterned pantsuit that bared her taut midriff.

Click the gallery to see all the red carpet looks!