Summary
Thanos is one of the most powerful beings in the Marvel Universe, even without the aid of cosmic artifacts like the Infinity Gauntlet or the Cosmic Cube, and his official title within the hierarchy of the very fabric of reality explains exactly how Thanos reached this level of unfathomable strength.
From birth, Thanos was already incredibly strong due to his heritage alone. An Eternal born with Deviant syndrome (which was later explained to be a deliberate mutation to create the strongest Eternal), Thanos was effectively a mortal god when compared to the vast majority of lifeforms in the universe – including and especially those of Earth. However, his baseline power-set wasn’t enough for Thanos, as he spent the majority of his adult life (before becoming a prominent Avengers villain) seeking forbidden sciences which enhanced his body and mind in ways that he never dreamt possible. With every victory, Thanos slowly became something far greater than an Eternal, until he eventually claimed a title that granted him the greatest upgrade of them all: Avatar of Death.
Thanos Is The Avatar Of Death, Strong Enough To Kill Entire Universes
In The Thanos Imperative by Dan Abnett, Andy Lanning, and Miguel Sepulveda, the nightmarish Old Ones known as the Many-Angled Ones that invaded the Cancerverse, killing Death in their wake, breached the multiversal veil and had begun their invasion of Earth-616. To stop them, the Guardians of the Galaxy went with Thanos to the Cancerverse. Being the Avatar of Death, Thanos was able to literally bring Death back to that swirling hellscape of a reality, and Death Herself made quick work of the entities that eliminated her before. Thanos fulfilled his cosmic purpose of keeping life in-check as an effectively immortal bringer of Death, and in doing so, he displayed his full power.
Throughout this storyline, Thanos not only proved to be unkillable (which he initially took as Death’s rejection of him), but he was also quite literally Death’s right-hand man. In every way that matters, Thanos essentially aimed Death at an entire universe, and pulled the proverbial trigger to wipe out every trace of the Cancerverse’s unnatural life. This is an ability even some of the most obscenely overpowered entities in the Marvel Universe don’t have access to, with even Death Herself having been unable to do so alone. In fact, this power was so terrifyingly immense, that the Guardians of the Galaxy feared Thanos would use it against Earth-616 after the Cancerverse threat was eliminated, and opted to maroon him in the universe he killed. The only way the Guardians knew to stop Thanos after witnessing this moment, was to essentially crush him under the weight of a dying reality – that’s how powerful he became as the Avatar of Death.
Thanos has always seen himself as a harbinger of death, as his obsession with the living embodiment of Death has been something he’s lived with since he was a boy. However, it wasn’t until Death granted him the title of her living Avatar that he truly reached his peak, as that cosmic title reveals why Thanos is so powerful in Marvel lore.
