I had a JD with the top dorsal fin split in half (wouldn't call it a deformity though because it wasn't born that way)
Had a Koi with 1 eye, and a bent up tail.
Have a koi that looks like a stroke victim.
Have a koi with a slight bent upwards tail.
Also had a 2 ft pleco with a tail that was bent upwards at a 90 degree angle.