The following contains major spoilers for What If... Miles Morales #3, available now from Marvel Comics.
More than most other heroes, Miles Morales is intimately familiar with the possibilities that exist within the Multiverse. While the mainstream version of the hero has made a name for himself as a fan-favorite Spider-Man, there are plenty of other variants of the character just waiting to step into the spotlight. One such variation of the character has been endowed with the power of the Hulk, and uses his awesome power to inflict the ultimate punishment on an enemy, possibly saving his universe in the process.
What If... Miles Morales #3 (by Anthony Piper, Edgar Salazar, Chris Sotomayor, and VC's Cory Petit) joins Morales in a therapeutic session with Doc Samson. From inside Avengers Mansion, the two discuss the events that led Miles to his Gamma-induced transformation, as well as the struggles he has faced in the time since. Like nearly every other version of him across the Multiverse, this Miles' life was marred by the actions, and eventual loss, of his uncle Aaron, better known as the Prowler.
In this world, Aaron lost his life at the hands of Emil Blonsky, better known as the Abomination. At the sight of Aaron's murderer, Miles lost control of himself and killed his opponent. Now that memory and the knowledge of what he is capable of constantly hangs over the young hero, dragging him into a deep depression. However, despite the blood on his hands and the guilt he feels, Morales may have actually done his universe a huge favor.
First introduced in 1967's Tales to Astonish #90 (by Stan Lee and Bill Everrett), Emil Blonsky began his supervillain career while spying on the US military. After stepping into the path of one of Bruce Banner's experiments, Blonsky was bombarded with the same radiation that created the Hulk. Rather than turning towards heroics, Emil instead joined the ranks of Marvel's most menacing monsters as the Abomination. While his efforts have largely been focused on antagonizing the Hulk, Blonsky has also been behind several far worse plots.
The Abomination has made a reputation on the back of his unthinkable cruelty just as much as his incredible strength. In 1998's Incredible Hulk #466 (by Peter David and Adam Kubert), Blonsky used his radioactive blood to murder the hospitalized Betty Ross, all to ensure that her marriage to Banner would end in tragedy. As bad as that was, it paled in comparison to Abomination's more recent attempt to take over the world with an army of unwitting Gamma-irradiated zombies. Thankfully, the heroes of Gamma Flight were there to put an end to the horror and foil the attempt of the monstrous madman.
No matter how haunted he is by his actions, Miles probably did the right thing at least when considering the typical trajectory of Abomination's story. Of course, there is always the matter of Gamma Mutates' innate immortality. Even the Blonsky of the primary Marvel Universe has clawed his way back to the land of the living on multiple occasions. Chances are that his death in the world of What If... Miles Morales won't be any more permanent than any of the others. Regardless, that takes nothing away from the fact that the action Morales took to destroy Blonsky undoubtedly spared his world of much unnecessary suffering.