When you think about the best Jedi hunters, it's the Grand Inquisitors. They work for Darth Vader and they led the attack which carried out order 66 which moved to eliminate all Jedi that might be a threat to the empire.
The Grand Inquisitor is one of biggest villains in the Star Wars franchise. He killed way more Jedi from hunting them down. Third Sister thought she was going to replace him but she way out of her league.
The Grand Inquisitor even though he was killed still managed to find a way to cling onto the dark side by having his life form turned into a Sentinel of the Dark Side,. He kept on serving the Emperor Palpatine in the afterlife.
