Robert Liston was a pioneering Scottish surgeon known for the only operation with a 300% mortality rate (though this may be apocryphal).
Amputated the leg in under 21⁄2 minutes (the patient died afterwards in the ward from hospital gangrene; they usually did in those pre-Listerian days). He amputated in addition the fingers of his young assistant (who died afterwards in the ward from hospital gangrene). He also slashed through the coat tails of a distinguished surgical spectator, who was so terrified that the knife had pierced his vitals he fainted from fright (and was later discovered to have died from shock)
- Richard Gordon
His Wikipedia page also mentions accidentally cutting off a patient's testicles "in his enthusiasm", and holding his surgery knife between his teeth to keep both hands free.