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 her death, Fenris was resurrected by Hela with the Eternal Flame and put at her service during her rule over Asgard, but Fenris fell into the vastness of space during her battle with Hulk.

Conquering the Realms
"We were unstoppable. I was his weapon in the conquests that built Asgard's empire. One by one, the realms became ours"

- Hela to Skurge

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
"With the Eternal Flame, you are reborn!"

- Hela

Following her death, Fenris' corpse was buried deep beneath Odin's Vault along with the corpses of the fallen Berserkers, and remained there for centuries as the beast's very existence was wiped out of Asgard's history by Odin. Nevertheless, when Fenris' mistress Hela returned from her banishment following Odin's death, she used the power of the Eternal Flame to reanimate Fenris as well as the Berserkers. Fenris would later be used as a means of intimidating the Asgardians when Hela and Skurge went in search of the stolen sword Hofund.

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

- Valkyrie

As Heimdall guided the surviving populace towards his observatory, he spotted Fenris and an army of Berserkers guarding it from a distance. Fenris led the charge towards the Asgardians before Valkyrie shot at her from the Commodore, but the gun had no effect on the giant wolf. At this point, Fenris resumed charging towards the Asgardians. Just as she was about to attack, Bruce Banner hit the bridge in front of her. Fenris paused to sniff the unmoving body. Deciding he was no threat, Fenris prepared to attack, but was suddenly dragged back by her tail and thrown away. Fenris met her 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 her massive jaws open. Eventually, she snatches Hulk up in her jaws and dunks him in the water, and bites painfully into Hulk's highly impervious skin. Hulk punches Fenris off and Fenris falls down the waterfall into the void to her 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, only preparing to face it once he knew it was absolutely necessary.
 * Superhuman Strength: Fenris has tremendous strength that can match that of the Hulk, which allowed her to engage the latter in a brief, albeit vicious battle. Fenris' immense jaw strength allowed her 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 her mouth.
 * Superhuman Durability: Fenris is highly invulnerable, as she was unscathed after getting shot at by Asgardian ships, and even after battling the Hulk.

Allies

 * Hela † - Mistress
 * Berserkers †

Enemies

 * Surtur †
 * Asgardians - Former Allies
 * Odin †
 * Heimdall †
 * Skurge †
 * Einherjar †
 * Sleipnir
 * Revengers
 * Thor
 * Bruce Banner/Hulk - Attempted Victim and Killer
 * Brunnhilde/Valkyrie - Attempted Killer
 * 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. He is based on the Norse wolf god.
 * Unlike his mythological and comic book counterparts, the Marvel Cinematic Universe's version of Fenris is a female.
 * Fenris and Abomination are the only characters in the Marvel Cinematic Universe to have pierced Hulk's tough skin.