Sheev Palpatine of Naboo was the public name of the Sith Lord Darth Sidious. After serving as representative of Naboo in the Galactic Senate for twenty years, he orchestrated a series of events that led to him being elected Supreme Chancellor of the Senate and receiving broad emergency powers to fight the Clone Wars against the Confederacy of Independent Systems. By the end of the war, he had accumulated enough political power to reorganize the Galactic Republic into the Galactic Empire and declare himself Emperor.
Skills and Abilities
Although he prefered to manipulate from behind the scenes, Palpatine was also a deadly fighter, dispatching three of the four Jedi sent to arrest him in a matter of seconds, before being defeated by the fourth, Jedi Master Mace Windu (arguably the most powerful warrior in the Jedi Order). However, Palpatine had so manipulated events that Anakin Skywalker turned on Windu and allowed him to regain the upper hand. It is unknown whether he foresaw this outcome, or simply got in over his head and then got lucky. Palpatine then went on to duel Jedi Master Yoda in the Senate rotunda, a fight from which Yoda eventually withdrew, leaving Palpatine's rule without effective challenge for over twenty years.
Perhaps Palpatine's farthest reaching goal was the pursuit of immortality itself, and it was partly with the promise of overcoming death that he lured Anakin Skywalker to his side. Palpatine eventually learned to transfer his consiousness to a clone body, thus surviving his seeming death at Anakin's hands during the Battle of Endor. The reborn Palpatine reached the height of his powers during the events portrayed in the Dark Empire comics, during which he created powerful "Force storms" and slowly drained the life from his servants on the planet Byss. At his most powerful, Palpatine was able to hide the presence of the SSD Lusankya on Coruscant, possess other sentient beings, and grant Force powers to others. Combined, these abilities and others suggest that Palpatine was probably the most powerful Force-user to ever exist, barring perhaps Luke Skywalker and (in unrealized potential) Anakin Skywalker.
Palpatine's Sith name is often misspelled as Darth Sideous.