Wolverine has long been one of the strongest Marvel heroes ever, as his adamantium claws and ability to survive pretty much anything thrown his way make him a formidable foe. However, Wolverine once received a sizable upgrade making the hero the new wielder of the Phoenix Force, one of the greatest cosmic weapons of all time, turning Logan into one of the most powerful forces in history.
The Phoenix Force is an ancient cosmic entity representing life, rebirth, and destruction in the Marvel Universe. It originally starred in the Dark Pheonix Saga, where Jean Grey became possessed by the Phoenix Force and became the titular Dark Phoenix. In the role, she lost control of her powers and ultimately sacrificed herself after killing billions of lives after absorbing the energy of an alien planet's sun. Recently, Marvel heroes, including Wolverine, competed in a tournament in the most recent arc of the Avengers, with the winner getting the powers of the Phoenix. Echo was deemed the winner and givens its immense cosmic powers.
In Thor #5 (2018) by Jason Aaron, Christian Ward, and VC's Joe Sabino, King Thor found himself at the end of the universe searching for signs of life when he encountered Wolverine, who possesses the Phoenix Force. However, Logan wasn't the same hero the God of Thunder once knew. Instead, Wolverine had long abandoned his superhero moniker, as he hadn't used the name for hundreds of thousands of years. Thor wonders what his former ally had been up to since they last met, and Logan reveals he's become a "cosmic cowboy," taking out Celestial beings as the universe ends.
Thor is stoked to see his friend, but after suggesting they save the heavens together, Wolverine attacks him and says things are unfolding as they should. He tells Thor he "knows when to let things die" and says it's time for the universe to meet its end. Thor sends Mjolnir through Wolverine's chest, but when he recovers, Doctor Doom (wielding the powers of Iron Fist, Doctor Strange, Ghost-Rider, and Starbrand) uses his combined powers to try to kill him. Wolverine sacrifices himself to boost Mjolnir and create a weapon possible of killing Doom. Thor then begins a near-Century long fight with the villain and ultimately defeats him.
The arc of Thor is one of the most insane, badass runs on the character ever. At the end of the universe, Marvel's greatest powerhouses duked it out. Thor tried to save everything while Wolverine wanted to let it all finally die. In the end, Wolverine sacrificed the Phoenix Force to allow Thor to carry on the fight. After hundreds of thousands of years, Wolverine - with some of the greatest cosmic powers -realized his time was up. It was a legendary way to go out.
