In anime, or manga, they are characters who begin the series as an antagonist. A mayadere will fall in love with the main character, but that doesn't mean they will switch sides, and are willing the kill their love interest if they feel betrayed.
An example of this is a specific character in Akame Ga Kill, her name is Esdeath, and you should watch that anime.

Weeb1: "NE NE, Watashi Wa Think That One Waifu From (insert-anime-that-has-{loli}), Is Kawaii..."
Weeb2: "Nani? Omae Wa Gay~desu, Watashi Only Go For Evil Waifus..."
Weeb1: "Anata Wa Mean A Mayadere?"
(TRANSLATION)
Degenerate1: "Hey Hey, I Think That That One (false-2d-girl) Waifu From (insert-anime-that-has-(an-underaged-girl)), Is Cute..."
Degenerate2: "What? You're Gay, I Only Go For Evil (false-2d-girls) Waifus..."
Degenerate1: "Do You Mean A Mayadere?"
by AnonymousUser177013 January 29, 2019
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Character that starts off as a villain but ends up in love with the hero.
Mayaderes usually joke around with their former enemy by saying things like ''Die'' or ''I will kill you''
Konjiki no Yami is a mayadere from the series To LOVE-Ru
by Crabmain September 4, 2017
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