Jennifer "Rad" Burke
It can be argued that Dusty shares much of the blame for Jennifer's hard feelings toward her, but Rad herself can be said to have driven her husband, David, into the arms of another woman. Ultimately, who is at fault doesn't really matter as even a seemingly rehabilitated Rad doesn't regard her former compatriot with anything that could be mistaken for warm affection.

General Proxima of Rur

Constantly being on the losing end of every battle against Dusty, losing her position as commander of the Rurian armed forces, and being banished from her home planet, have done nothing but fuel Proxima's hatred for Stardust and anyone who aligns with her.

 Proxima and Stardust have a history that goes way back. Even before the Rurian civil war, the former head of the planet's military despised the "soft" nature of her planet's most esteemed scientist.