Sugilite

Sugilite is a three-Gem fusion in Steven Universe, formed by combining Garnet, Ruby, Sapphire, and Amethyst. She is an unstable, massive, and destructive powerhouse who prioritizes raw strength and self-gratification over teamwork. Ruby contributes his hotheadedness, fiery temper, and emotional volatility, while Sapphire contributes her cold, distant demeanor and stubborn refusal to change her mind once it's made up. Amethyst contributes her recklessness, lack of inhibition, disrespect for authority, and addictive thrill for the sheer power of fusion. Rather than balancing each other out, their worst traits amplify, creating an aggressive and egocentric personality that becomes so consumed by her own power that she forgets her individual identities. Garnet and Amethyst initially fuse into Sugilite to destroy a Warp Stream tower, but they enjoy the feeling of being large and unstoppable so much that they refuse to unfuse. Sugilite eventually goes on a rampage and accidentally puts Steven in danger. Pearl outsmarts the massive brute through strategy rather than brute force, causing her to fall and separate back into Garnet and Amethyst. Sugilite is summoned a second time to destroy Homeworld's communication hub, which Peridot is rebuilding. She appears larger during this appearance but remains fused for a much shorter time, immediately separating after completing the job.