Tyga
Tyga was Kylie's first real boyfriend. He made some appearances on the show, but it was usually just for drama. At the time, Tyga was at the height of his rapping career. He was made even more famous for dating the youngest Kar-Jenner when she was of age. Honestly, their relationship was creepy.
That Was His Peak!
Most fans can agree that dating Kylie was his peak. He's gone somewhat downhill since then and hasn't had a decent hit song in a while. There's also the drama of between him, Kylie, Rob, and Rob's baby mama, Chyna, who was also Tyga's baby mama. If anything, most of his career consisted of getting involved with two powerful ladies.