Corrupting the Innocent

In many stories, there comes a time when the villain Corrupts the Innocent, usually the hero or someone he or she cares about in many ways:
 * Turning innocent people against each other
 * Persuading the hero to let his hatred and anger get the better of him
 * Pitting the hero against someone he loves
 * Training him the wrong way

Examples

 * Terry Silver convinces Daniel LaRusso to turn away from Mr. Miyagi and turn to him for training.
 * Rex Pester turns Drew Pickles against his brother.
 * Scorpion turns Monkey against Po.

Quotes
"Hey, Mr. Pickles, how does it feel knowing your brother lost your only daughter? (Drew Pickles, breathing fire: HE WHAT?!) Share your pain."

- Rex Pester turning Drew Pickles against Stu to get his money.