Surtur

"'Ragnarok...has begun!'"-Surtur upon hearing of Baldur's death

Surtur  is a Fire Demon and ruler of  Muspelheim, Realm of Fire Demons. He appears on Midgard after Kratos accidentally causes Fimbulwinter to happen early, destroying most of the planet until he is killed by Kratos and Hulk.

History
He is first seen confronting Thor in Muspelheim, siccing his Fire Demons on him, but the God of Thunder easily slaughters them before hurling Mjölnir at the Fire Demon King, sending him plummeting into the depths of Muspelheim, allowing Thor to escape.

Surtur recovers from his confrontation with Thor and upon seeing the Bifrost open, sends a large horde of his Fire Demons through it, which sends them to Midgard, Realm of the Mortals. Upon arriving, they are attacked and easily destroyed by Hulk, much to Surtur's anger and frustration.

Personality
Surtur desires the destruction of all the Realms through fire and depends on his lesser Fire Demons to do what he pleases. He has a no-nonsense attitude and gets infuriated when nobody takes him seriously.

Physical Appearance
Surtur is a massive Fire Demon that easily towers over the others. His body is well-built and appears to have tremendous strength. His body is red and his hair is made of flames. He also has a pair of large horns on his head and he does not have bat-like wings and tail, which he refers to as a 'crown', though many characters are quick to say it isn't a crown at all.

Powers

 * Fire Demon Physiology: Surtur was one of the most powerful beings in the Nine Realms and the cosmos, powerful enough to challenge and almost overpower Thor even in a weakened and battered form; however in his limping, weakened state he eventually proved to be weak enough for the Asgardian Prince to defeat him using superior skill. This makes him one of the most powerful beings in the Nine Realms and the cosmos, with Odin being the only confirmed being to surpass his might.


 * Fire Manipulation: As a Fire Demon, Surtur can generate massive waves of fiery energy from his Twilight Sword to engulf his targets in flames. This fire was strong enough that in his weakened state, he was able to force Thor using his hammer back and make him struggle. Upon reaching his full might, Surtur's flames would be able to engulf the whole of Asgard itself.
 * Superhuman Strength: Even while weakened, Surtur was still strong enough to challenge Thor. After being restored to his true form from the Eternal Flame, Surtur regained full strength and was tremendously increased to incalculable superhuman levels, to the point that he effortlessly swatted away a leaping Hulk. However, Surtur is notably not as strong as Odin, as the latter was successfully able to defeat him and take away his Eternal Flame.
 * Superhuman Durability: Surtur's weakened level of durability is already great enough to withstand blows from Thor using Mjølnir, taking a full-powered electrically charged hammer blow to the head to kill him, but after being revived from the Eternal Flame, he became practically invulnerable, only for Hulk's blows to fatally harm him. However, he is still vulnerable to beings of superior power like Odin, who defeated him so grievously that Surtur remained in a battered and limping state for approximately five thousand years.
 * Longevity: Surtur is effectively ageless, as his body does not age, which has allowed him to live for thousands of years.