Backstab Backfire/Playing With

Basic Trope: A good guy beats a bad guy, and then the bad guy tries to kill the good guy when his or her back is turned! The hero is able to successfully defend against the attack, possibly killing the villain in the process.
 * Straight: Alice fights Evil Elliot and wins. She has mercy on the poor, defeated, seemingly helpless wretch and begins to walk away. Elliot tries to stab her in the back, but Alice dodges the knife thrust and buries her own blade in Elliot's chest before he can try again.
 * Justified: Alice is willing to forgive, but promised Evil Elliot that the next time he did anything evil, she would kill him. And she always keeps her promises.
 * Inverted: Evil Elliot is the superior fighter and has defeated Alice, who is the hero. Elliot is very evil, but nevertheless he just doesn't feel like killing Alice right now, so he starts walking away. Alice can't let such a dangerous person run free, so she desperately rushes at him from behind...and is promptly dispatched by Elliot.
 * Subverted: After his defeat at the hands of the mighty Alice, Evil Elliot runs at her from behind with his blade drawn, but he doesn't expect or intend to hurt Alice by doing so. He is actually hoping that Alice will kill him, because Elliot is a Death Seeker.
 * Double Subverted: Evil Elliot runs at Alice from behind with his blade drawn, feeling certain that Alice will react to his very loud and obvious attack by killing him and ending his miserable existence. However, Elliot slips in a pool of his own blood and stumbles, inadvertently dodging Alice's decapitating slash. Then he bounces off the opposite wall and crashes into Alice dagger-point first, killing her. Oops.
 * Deconstructed: Alice's act of sparing Evil Elliot is a wile. She was hoping for him to try to backstab her from the beginning. This would give Alice a perfect justification to kill Evil Elliot and remain a pure heroine in the eyes of everybody and/or avoid the moral implications of killing a downed opponent.
 * Averted:
 * Evil Elliot accepts his defeat and allows Alice to take him to the cops who are waiting outside to arrest him.
 * Defeat Means Friendship
 * Evil Elliot succeeds in killing Alice when she's off-guard.
 * Lampshaded: "What were you thinking, Elliot? Have you ever heard of this actually working?"
 * Invoked: "Don't turn your back on him, Alice! He looks like he wants to stab somebody and probably still has a weapon on him somewhere!"

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