What is the name of the Supreme Leader before Kylo Ren takes over?

The story behind the answer

He is the Supreme Leader of the First Order in The Force Awakens and The Last Jedi, commanding figures like General Hux and manipulating Kylo Ren. Palpatine ruled earlier as Emperor of the Galactic Empire, not the First Order; Vader was Palpatine’s enforcer, never a political leader; and Hux, despite his authority, remains a general under the Supreme Leader.

Introduced as a shadowy figure who seduces Ben Solo to the dark side, he oversees the rise of the First Order and the use of Starkiller Base. His downfall comes when Kylo Ren kills him and claims leadership. The Rise of Skywalker reveals he was a manufactured puppet tied to Palpatine’s contingency plans on Exegol, adding a twist to his seemingly independent power.