Possessed or Brainwashed

Heroes gets many of these. Demons or spirits goes inside the heroes bodies to control there body for hurting a friend, killing someone, wants a body period, saying or warning something to a person they knew or a different person, or kill the heroes inside there body. Sometimes heroes want the demon or ghost to possessed them so they can have a better life or get powers or revenge. Now brainwash people tell them like for example that you lost a friend, home, family, family backstab you or a friend, the villain wants them as their henchman. Their a lots of ways of being possessed and being brainwashed. Also hypontize someone can leads to brainwashed.

Examples

 * Ryou Bakura gets possessed by an evil entity living in the millennium ring. Which is in fact Zorg himself, but he is just called Yami Bakura.
 * Ichigo Kurosaki has two zanpakutos inside of him, one is a good one and the other is an evil one. The evil one is Ichigo inner hollow. He thinks that Ichigo is the king while he is a horse. But when he posses him, he loves going for a fight and killing.
 * Princess Luna has this, she though Princess Celestia was getting more of the attention of being princess which leads her jealously turns her into Nightmare Moon.
 * Rarity has this, the shadow ghosts were looking for an easily target on the mane 6 looking in their dreams for weakness or nobody wants them. Rarity however was dreaming about her friends that they don't want her anymore, which leads the shadow creatures to turn her into their queen, Nightmare Rarity.
 * Twilight Sparkle has been possessed by the magic in her device, which makes her turn into Midnight Sparkle, but with her rampage this was Principal Cinch fault because she wants to cheat and win the games.
 * Vegeta has this, he yells at Goku saying that he should be at the tournament defeating Goku, which makes Dabura cancel the match and tell Babidi about Vegeta having an evil side and telling the others about the new recruit, and Babidi uses his magic to mind control Vegeta and transform him into Majin Vegeta.
 * Jaden gets possessed by The Supreme King because the reason why because of his feelings and trust of his friends and losing them.
 * Yami Yugi gets possessed by the Orichalcos by drawing its card. Yami Yugi became ruthless, savage, and so brutal to his monsters, and also want his enemies dead.
 * Ashi gets possessed by Aku when Aku reveals that Ashi is her biological daughter and corrupts her.
 * Fugitoid posseded by Overmind
 * Cynder in Dawn of the Dragons and first game of Spryo. When she was an egg Malefor goons took her in and Malefor made Cynder his servent by corrupting her with his magic. She gets corrupted again when she is going to fight her master, which leads her to attack Spryo.
 * Spryo gets corrupted two times. In Etneral Dawn and Dawn of the Dragons. The second game part is where he going to fight Ghaul. But he was knocked in where Malefor makes dragons evil. Spryo became cold blooded pin his dark form. Now in the third game he became corrupted again because his mentor sacerfice himself to save him and Cynder, which leads him to get angry which Cynder calmed him down.
 * Danny Phantom has been hypontize by Freakshow staff. Which leads Danny Phantom and the other kind ghosts as minions to do Freakshows bidding by stealing jewels and money. Also he makes Danny Phantom and his minions to do his bidding to attack someone too.
 * In Dragon Ball Xenorverse 1 and 2 the main heroes were you built and customize them, they get brainwashed by villains a lot, when you start playing through the games.
 * Gumball gets possessed by a spirit called "Jealousy", which it makes him jealous over Leslie because he thinks Penny and Leslie are dating.
 * Regan MacNeil