I've been a TLC fan forever. IMO, they were all beautiful.
All members slayed equally and uniquely to me. And they all peaked/came into their own at different stages.
Chilli was the pretty girl, exotic one from the beginning.
TBoz began to slay during CrazySexyCool with the short bob, smooth style, and sexiness that made her the star at that time.
Left Eye came into her own as a woman and matured in her looks by the time Fanmail came out. Really, I think Ladies Night and slaying that MTV Awards sexy costume did it for her. In Fanmail, the Donnell Jones video, etc, she was really bringing her sexy bohemian, futuristic tea that made her the interesting one visually during that era.
In a nutshell, they all complimented each other and had unique beauty that flourished at different times.