Freedon Nadd is one of the few people on the list without the "darth" tag, but he was one of the greatest Sith ever. People often forget about him because he is by no means highly publicized like so many others. However, he might have been one of the few
on this list who left a lasting impression, as his decisions affected generations to come.
He was first a Jedi prodigy that they wanted to mold into one of the greats, which seemed easy because of his immense talent. However, there was something dark about him and his gifts and it was revealed in full when he began training to become a Jedi. Nadd trained on planet Ossus where many others spent their time. He trained under Master Matt Tremayne, but lusted after the power he had. He ended up killing his master and went on to renounce his Jedi affiliation.
Nadd didn't just go into hiding after this ordeal. In fact, he went to the very heart of the Sith Empire where he attained a great deal of dark knowledge. Nadd was a very selfish man and wanted all the power he could have.
Nadd declared himself the Dark Lord of the Sith. No man offered it and no master freely gave this title to him. This didn't sit well with many, but due to Nadd's immense power, few could stop him. He went on to conquer the world of Onderon where he led until his physical demise after over one hundred years on the throne.