Confirmation Sidious > Snoke
From StarWars.com.
The Supreme Leader of the First Order, the mysterious Snoke was powerful with the dark side of the Force, and seduced Ben Solo into abandoning the Jedi path to become his apprentice. He also commanded the technological war machine engineered to destroy the New Republic and the Resistance. Kylo Ren turned on his master and killed him, but would soon learn that Snoke had been a mere puppet, created and controlled by a more powerful master of the dark side.
Snoke ordered Kylo to complete his training by killing Rey, exulting at the resolve he sensed in his oft-conflicted apprentice. But Snoke’s visions and Force senses had betrayed him. The former Ben Solo ignited Luke Skywalker’s lightsaber, cleaving his master in two and ending Snoke’s life. Kylo thought he had destroyed a key part of the past that tormented him, but would soon discover Snoke had been created and controlled by a more powerful master of the dark side, as part of a sinister scheme set in motion decades earlier.