Spinel

Spinel is the main antagonist of Steven Universe: The Movie and a supporting character in Steven Universe Future.

She was created 6,000 years prior to the events of the movie to comfort the lonely Pink Diamond who had lost her first Pearl to White Diamond. The two would play in Pink's garden until she was finally given a colony. At this point, Pink outgrew Spinel and abandoned her under the guise of playing a game by having Spinel stand alone for thousands of years while Pink never returned.

After discovering this through Steven's message to the universe she went to Earth with full intent to destroy all organic life forms as a way of getting revenge.

After making amends with Steven and the Crystal Gems, the Diamonds take her back to live with them on Homeworld. Now reformed and free, she is still living with the Diamonds, living a less destructive and aggressive life.