Darth Angrus

Darth Angrus born Jaden Korr, was a Jedi Knight who fell to the Dark Side and became Dark Lord of the Sith, after Korr killed his best friend Rosh Penin out of anger he made Alora his Sith Apprentice, and the two went to Korriban and killed off the Jedi and Sith. Angrus then established a new Sith Order and attempted his war against the New Republic and New Jedi Order.