Leslie and Mark
Before Ben Wyatt came into the picture, Leslie and Mark had a thing. Mark as well as the dynamic between him and Leslie was a huge part of season one of the show. This relationship wasn’t so compelling or enjoyable though, and Mark didn’t deserve Leslie.
Source: The Whisp
The first season of the show was actually kind of rough, thanks to Mark. Luckily, he was written out of the show and Ben Wyatt was written in. And everyone likes Ben.