Darth Mayrik

Darth Mayrik was a female Human/Echani Sith Lord who was active during the waning days of the Galactic Empire and the rise of the New Republic. She worked throughout the Outer Rim and even worked within the Republic and was extremely active in galactic politics before her death in 25 ABY at the hands of Luke Skywalker. Mayrik was a footnote in Galactic History, but her murder had large sweeping effects on the galaxy at large. Her daughter's desire for vengeance led to the destruction of the Jedi Order and the fracturing of the Republic, as well as the subsequent paradigm shift that left the galaxy less open to conquest. Her murder also partially inspired the later Sith resurgence that saw them become the dominant group of Force Users in the galaxy.

According to 2V-R8, Mayrik was exceptionally powerful and skilled in both the Force and lightsaber combat, and at the height of her power was the most powerful Force User alive. It was only because her daughter's safety meant more to her than anything that Luke Skywalker was able to kill her.