Darth Nihilus [Sith Lord Of Hunger]
The Lord Of Hunger one of the most feared dark lords to have ever existed, his command over the force and those that wield it is in many ways ridiculous. The Sith Lord could drain entire planets of life using his mind and feed off the death of all those who lived on it. I believe Nihilus ranks above the most forceful Sith that have ever lived.
Nihilus is less than a man and barley alive at all being that a large part of him is being dark side energy. He was a ok duelist and could use force lighting and a powerful force push, when Nihilus was only a man he was one of the last surviving members of Darth Revans Sith Empire and after experiencing the effect of the mass shadow generator he was transferred into something else less human, the effects caused him to desire force energy and gave him the ability to do so, he became a wound in the force and his presence echoing throughout the galaxy.
Finding the Sith Lord Traya, Nihilus learned to control his feeding, this ability he learned would be known as force drain and was the only Sith to truly control and master this power. The amount of force energy he would take in would change him and take over his body and he would become dark side energy itself, this resulted his physical self to leave the world and that is not what he wanted in order to feed he had to remain in the physical world and took great measures to make sure he stayed there. He used his mask to fuse his spirit within it allowing his physical body to move on and for his sprit and consciousness to continue to feed.
As he fed more and more so did his power to the point where all feared him even his own master thought that she could not control him (Darth Traya) and he would continue to feed until the whole galaxy had been devoured and this was his only desire. He than partnered up with the Lord of Pain Darth Sion to overthrow their master Darth Traya so that she could no longer hold him back from his desire, together Sion and Nihilus worked together to drain Traya and sever her connection to the force.
Because of his growing power the Jedi counsel met up on a planet to discus the Sith Lord. While on the planet, Darth Nihilus drained all the planets force energy killing all but one, this one was a woman named Visas Maar and became a slave to Nihilus. Visas Marr along with Traya and the exiled jedi Meetra Surik, had come up with a plan to destroy the Sith Lord, Meetra Surik was also a wound in the force so she was able to with stand Nihilous's power and with the help of the madalorians and remaining Jedi, they successfully killed Nihilius aboard his ship the Ravenger. The exile was able to counter him with light as again she too was a wound in the force and was immune to his power and was able to beat him easily in force and lightsaber combat. Nihilius spirit and physical body still remained fused in his mask and robes and it would remain on Korriban where he would rest, to weak for him to ever return.
Nihilius only had one ability he ever used and that was force drain so powerful that it could destroy worlds and fighting Meetra Surik was the only time he encountered someone that was immune to it and thus leading to him to use the only other thing he could do and that was lightsaber combat which would lead to his down fall because he was not a very skilled duelist. but he is extremely unbeatable if any sith or jedi challenged him all he would do is drain their force energy and their life away and they would not have enough time to react to such a thing but in the rare chance you are immune or can withstand it then he is extremely beatable.