Fenris

"Fenris, my darling, what have they done to you?"

- Hela

Fenris was an Asgardian Wolf who served Hela during the times of the expansion of Asgard around the Nine Realms. Millennia after his death, Fenris was resurrected by Hela with the Eternal Flame and put at her service during her rule over Asgard, but Fenris was ultimately hurled into outer space by Hulk.

Conquering the Realms
Fenris served Hela as her loyal companion and mount during the expansion of Asgard around the Nine Realms. Fenris died some time after Odin exiled Hela.

Resurrection
Following his death, Fenris' corpse was stored under Odin's Vault, right up until his mistress, Hela, resurrected Fenris, in a blast of green infernal energy. He was later seen with his mistress as she and Skurge round up civilians.

Battle at the Rainbow Bridge
"This stupid dog won't die!"

- Brunhilde

As Heimdall led the surviving populace towards his observatory, he spotted Fenris guarding it from a distance. Fenris charged towards the Asgardians, Above, Brunhilde shot at him from the Commodore, but the gun had no affect on the giant wolf. At this point, Fenris resumed charging towards the Asgardians. Just as he was about to attack, Bruce Banner hit the bridge in front of him. Fenris paused to sniff the unmoving body. Deciding he was no threat, Fenris prepared to attack, but was suddenly dragged back by his tail and thrown away. Fenris met his challenger, Hulk, in battle by charging him and attempting to devour him whole, but only succeeded in tossing them both into the waters below. Later, Fenris is seen leaping towards Hulk, trying to devour him again, but Hulk keeps his massive jaws open. Eventually, he snatches Hulk up in his jaws and dunks him in the water, and bites painfully into Hulk's nigh impervious skin. Hulk punches Fenris off and Fenris falls down the waterfall into the void to his second death.

Powers

 * Asgardian Wolf Physiology: Fenris, as an Asgardian Wolf, and the personal pet of the Goddess of Death Hela, is one of the most powerful and fearsome beings in the Nine Realms, to the point that even Heimdall showed visible signs of fear when cornered by the beast on the Rainbow Bridge.
 * Superhuman Strength: Fenris has tremendous strength that can match that of the Hulk, which allowed him to engage the latter in a brief, albeit vicious battle. Fenris' immense jaw strength allowed him to bite through Hulk's immensely durable flesh, causing Hulk to bleed, as well as to lift and throttle him around like a rag doll in his mouth. Indeed, Hulk would only win by hurling Fenris off the edge of Asgard, into outer space.
 * Superhuman Durability: Fenris is nigh-invulnerable, as he was unscathed after getting shot at by Asgardian ships, and even after battling the Hulk.

Allies

 * Hela † - Mistress
 * Berserkers †

Enemies

 * Surtur †
 * Asgardians - Allies turned Enemies
 * Odin †
 * Heimdall
 * Skurge †
 * Einherjar †
 * Revengers
 * Thor
 * Hulk - Killer
 * Brunnhilde/Valkyrie
 * Loki

Trivia

 * In the comics, the Fenris Wolf is a creature of Asgardian origin, and is said to be the offspring of Loki and the giantess Angrboda, and the brother of Hela. It is based on the Norse wolf god.
 * Fenris and Emil Blonsky are the only ones in the MCU to have pierced Hulk's tough skin.