I’m going for Jerec. Prosset Dibs is interesting, but Jerec was even more so; once the apprentice of Jocasta Nu, one of the Jedi Order’s most prominent scholars who never took part in the Clone Wars. It was also said that Jerec’s embrace of the dark side rivaled that of Darth Vader and he became one of the most powerful Dark Jedi in Legends. Plus, the Legends version of the Inquisitorius could put up more of a fight against surviving Jedi Knights and Masters compared to their Canon counterparts.