Purple Is Powerful

Anime & Manga

 * Lucoa from Miss Kobayashi's Dragon Maid is a former goddess and her magic circles are purple. Tohru's father also purple magic and is called "The Emperor of Demise".
 * Naruto:
 * In his fight with Sasuke at the Valley of the End, Naruto uses a purple variation of the Rasengan, as a result of the blue sphere of chakra being enveloped and supercharged by his red Tailed Beast aura.
 * Sasuke himself also possesses a purple Susanoo armor after he upgrades to Mangekyo Sharingan.
 * In Noir, purple is mainly associated with antagonists, including Altena, Chloe, and Silvana "Intoccabile" Greone, all of whom prove to be highly dangerous.
 * In Sailor Moon, Sailor Saturn is heavily associated with the color purple: her uniform has purple accents, her eyes are purple, even her magic is purple. She only awakens when there is a planet to destroy, a civilization to wipe out, or an Elder God to kill, solo. In her entire active history, she has only ever failed once.

Web Animation

 * Raven Queen in Ever After High, hermagic glows in purple, and she happens to be a daughter of an evil queen. Fortunately she isn't like her mother, but her power can get out of control and do some unexpected damages.

Western Animation

 * OK K.O.! Let's Be Heroes has Professor Venomous, a purple-skinned villain with a power level of -7.
 * Steven Universe:
 * Garnet, the leader of the gems, with a distinctly magenta color scheme that even shifts more towards purple later in the series. She's also the tallest of the current Crystal Gems, and both extremely strong and a Seer. The element of red and blue combined is also significant in that she is a fusion of the very red Ruby and the very blue Sapphire, who complement and match each other to such a degree that Garnet is basically a perfect fusion.
 * Incidentally, Amethyst of the same team has a violet color scheme, but isn't distinguished as particularly powerful — implications are even made that she's not as strong as she should be.