"Ax Crazy characters are someone who is psychologically unstable and presents a clear danger to others. Ax crazies are capable of extreme violence, whether carried out with a Slasher Smile, a Creepy Monotone, or out and out murderous rage, and with no way of knowing just what will set them off, this makes them extremely frightening to deal with. Also be prepared to expect them to burst out into insane laughter while undergoing the extreme violence. This mainly differentiates them from other eccentric characters who may themselves be obsessive, weird or seemingly crazy, but use this condition hand in hand with doing good, or at least not being in the way. However, some formerly established heroes can go through an episode of ax-craziness and still retain their heroic mantle."

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This has got to be the funniest trope name I've ever seen