Spinel

The unknown pink Gem is the antagonist of Steven Universe: The Movie

She is shown in the teaser trailer, main trailer, and poster for Steven Universe: The Movie, serving as the film's antagonist. She is shown to have the ability to stretch and change her form at will (similar to an old-fashioned cartoon), presumably just adeptness at shapeshifting. She has her gemstone, which is an upside-down heart shape, on her chest.