Thor may be Asgard's defender, but that doesn't necessarily mean he's its strongest warrior. In fact, in Marvel Comics, some characters have shown themselves to be even more devastating on the battlefield, and chief among them is a being known as the War Thor, who also happens to be a character fans of the MCU will recognize.
The horrors of war can break down even the strongest of soldiers, and it was one such event that broke the often jovial, rotund Asgardian warrior known as Volstagg. Traumatized by the loss of innocent children during the War of the Realms, this member of the Warriors Three answered the call of the unclaimed Ultimate Mjolnir, which had fallen to the mainstream Marvel Universe after the death of its Thor in Secret Wars. Believing that the Nine Realms needed a new kind of Thor, Volstagg - played by Ray Stevenson in the MCU - grabbed the hammer and was transformed into the War Thor, a familiar yet uncontrollable powerhouse that quickly became a threat to everything, whether it be ally or enemy.
Wielding considerable power and unquenchable bloodlust, the War Thor hunted his enemies to their homeworld of Muspelheim, where he challenged the Fire Giant Sindr, the Queen of Cinders. He used his weather controlling powers to bring down a torrential rainstorm in an attempt to drown the Fire Demon's entire population, an act of genocide stopped by Jane Foster as Thor. But her attempt to reason with and pacify Volstagg were drowned out by the hammer's influence, and their battle traveled multiple realms and even involved his old ally, the Odinson, who had also tried and failed to lift this Mjolnir originally.
Although a legendary Asgardian, Volstagg didn't have much of an identity in the MCU. In the comics, Volstagg is often treated as a comedic character - a glutton and coward - but one who always comes through in the end. Though killed in Thor: Ragnarok in the MCU before gaining much attention, this story reinvented Volstagg, pointing out that many of his flaws were ultimately desirable qualities in a friend, and reflecting on how much would be lost if he succumbed to his trauma.
Writer Jason Aaron not only redefined Volstagg but also the unique qualities of War Thor's hammer. In the past, Mjolnir was a magical instrument that allowed its user powerful abilities to use at their discretion as the mighty Thor. In this case, this Mjolnir was an alien entity, an object that had not only witnessed the death of its Thor but also the demise of its entire universe full of countless worthy souls. This Mjolnir turned its survivor's guilt into anger, the kind of anger that calls out for the kind of retribution that can only be found in war. Volstagg's fragile state allowed him to channel his rage and frustration, but at the cost of being just as ruthless and evil as his enemies, a price his friends were not willing to see paid.
In the end, Jane Foster's human form was enough to convince Volstagg to relinquish his hammer and return to his original state, although he would be held accountable for his actions. Volstagg would become War Thor once more to battle the vengeful Mangog, where he fought valiantly yet was defeated and his Mjolnir destroyed. Although his time as War Thor, much like his time in the MCU, was very short, Volstagg proved that despite his appearance and nature, he is not to be underestimated, either as a warrior or as a character with things to add to Thor's adventures.