The Orb (Marchen Awakens Romance) corrupted the benevolent witch, Diana's mind and persuaded her to abandon her homeland. Together the two formed the Chess Pieces and began their first steps in taking control of the world of MÄR.
Peta (Marchen Awakens Romance) was able to charm the leader of Luberia, Galian into joining the Chess Pieces by offering him power. After being recruited, Galian abandoned any care he had left for Luberia and allowed Peta to destroy the guild and everyone in it.
Orochimaru (Naruto) caused Sasuke Uchiha to betray Konohagakure by promising them power.
Sakazuki/Akainu (One Piece) has a talent for manipulating his enemies. During the Marineford War, he convinced Squard into believing Whitebeard had betrayed all his allies.
Jadis (The Chronicles of Narnia) induced Edmund Pevensie to betray his siblings via sweet talk, enchanted food, and empty promises.
As a bond-severing god, Shaga (Good Luck Girl!) can turn the best of friends and closest of allies, into the bitterest and most hated of enemies.
Darth Sideous (Star Wars) charmed Anakin Skywalker with his knowledge of the dark side causing him to betray the Jedi council and join the Sith.
Discord (My Little Pony: Friendship Is Magic) used his magic to corrupt Twilight's friends, causing them to turn against one another.