Surtur (Eternal Flame)

Surtur's powers and abilities

Fire Demon Physiology: Surtur was one of the most powerful beings in the cosmos, capable, even in his weakened state, of nearly overpowering Thor. After being resurrected by the Eternal Flame, Surtur's powers were immeasurably increased as he was finally able to bring Ragnarök to Asgard, destroying the incredibly powerful Hela in the process.

Superhuman Strength:

Even while weakened, Surtur was still strong enough to challenge Thor. After being resurrected at full power by the Eternal Flame, Surtur's strength was such that he was able to effortlessly swat away Hulk and quickly destroy Hela, who had herself been able to fight Thor and Valkyrie to a stalemate. Odin is the only being known to have been able to defeat Surtur at full power, having depowered, wounded, and banished him thousands of years ago.

Superhuman Durability:

Surtur was able to withstand blows from Mjølnir in his weakened state, only dying after sustaining a full-power electrically charged blow from the hammer to the head. Surtur's durability, with all his other abilities, increased massively following his resurrections by the Eternal Flame. In this state, Surtur was practically invulnerable, being only slightly phased by a leaping blow from Hulk and being only barely affected by Hela piercing him with an onslaught of huge blades. He also withstood a powerful shockwave that wiped the surface of the whole of Asgard. Odin, however, was able to severely wounded him at full power, leaving him battered and hobbled for more than 5,000 years.

Immortality: Surtur was effectively ageless, living as long as he needed in order to initiate Ragnarök, as recorded in a file from the Time Variance Authority called "Event Inquiry: Destruction of Asgard."

Fire Manipulation:

As a Fire Demon, Surtur can generate massive waves of fiery energy from his Twilight Sword. This fire was strong enough that, in his weakened state, he was able to hold his own against Thor. Upon reaching full power, Surtur's flames were strong enough to consume all of Asgard.