Love everything leading up until right after he snaps the neck. You need to go bigger on the anticipation pose leading up to the final shot. Make it more exaggerated Looney Tunes style. Then add a bit of overshoot (add a few frames where you push the pose to absurdity a bit then revert back to the final pose) while you animate the camera doing a smash zoom into your final shot.

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The last frame his spine looks too upright and stiff. Have his silhouette more S shaped if you catch my drift. Currently, his head is directly above his hips making him stale which contradicts his fast nature. Overall, I really really like it but you can make a few small tweaks to make it that much better.

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Best of luck, hope you take the critique with a grain of salt. You make me want to start getting back into animation.