The Finalizer was secretly built by the First Order in their "distant orbital factories" years after the Battle of Endor. It was in violation of the New Republic's disarmament treaties.
The Finalizer was a Resurgent-class Battlecruiser used by the First Order approximately thirty years after the Battle of Endor. The ship was under command of General Armitage Hux during Kylo Ren's assault on the planet Jakku in an attempt to obtain Luke Skywalker's hiding position from a member of the Resistance. When the Resistance fighter, Poe Dameron, was captured during the assault, the Finalizer remained in orbit during his interrogation.
During Poe's escape, he and the deserting Stormtrooper, Finn, stole a TIE/sf space superiority fighter from one of the vessel's hangers and managed to disable the Finalizer's turbolasers. During their escape, the Battlecruiser was only able to seriously damage the TIE, without fully destroying it. It was later present when Starkiller Base fired on the Hosnian system, with Kylo Ren watching the blast from the ship's bridge.