Terminal Redux by Vektor.

In the future, the leader of multiple military projects gets unwillingly deployed on a suicide mission (unbeknownst to him) by his superiors. The attempt at his death fails, and while he is stranded in the abyss of space, he discovers the secret to immortality. He returns to his home planet filled with rage and wants revenge. He slips into a power-hungry state and subsequently takes over both worlds in the story, transforming them into his own dictatorship. Eventually, after he has obtained all military, political, and overall power over these two worlds, he goes insane and realizes the insignificance of all this power he has achieved within the grandeur scheme of the universe and time. He decides to put an end to his reign by destroying his empire himself, simultaneously attempting to warn future generations and other worlds of the dangers in doing what he has done; encouraging them to learn of his story to avoid the same colossal tragedy that he caused himself. The story ends with him sacrificing his soul to the same star/celestial-being that gave him the power of immortality in order to truly destroy his regime once and for all.

It is an approximately 70-minute epic album filled with some of the most intense, progressive, technical, badass, and downright beautiful metal I have ever heard in my life. It has elements of thrash metal, black metal, death metal, and is one of the most sophisticated metal albums of all time. It is a complicated story, so I may have gotten some parts wrong or forgotten some crucial parts, so here is a link for its story explained: Terminal Redux