Because he is, if you think about it, sort of a main villain of the show.
No need to be mad about some facts: everything that went bad in 'The Umbrella Academy' happened because of Viktor Hargreeves, the family's Number Seven, triggering the apocalyptic events. Obviously, the blame is also on Sir Reginald Hargreeves, who was many things but a great father.
However, there is a way for Viktor to "redeem" himself after causing the explosion of the Moon in season 1 and kickstarting an alternate timeline at the end of season 2. After being the reason for things going wrong in two previous seasons, the most beautiful way for Viktor to make it up would be to simply save the world this time – instead of ending it. Again.
No big deal there.
"Who would’ve thought the man who ended the world (twice) would be the one working the hardest towards peace?" – @hotelhargreeves.
In one of the teasers for season 3, Viktor is seen doing his best to try and bring the family… well, families together to fix the time paradox that occurred after the chaotic siblings prevented the world from ending in the 1960s. His role as a peacemaker appears to be falling into place with how things have been working out for the Umbrella Academy. Basically, it was Viktor who brought the family together – albeit by making the siblings collaborate to stop the apocalypses he caused.
Notably, Viktor turns out to be an amazing mediator when is not blamed for all evil in the world by the ones he loves. He only unleashed his deadly powers when on the edge and desperate, or after being tortured for an extensive amount of time.
So maybe people in 'The Umbrella Academy' should finally consider the idea of not treating Viktor Hargreeves like an atomic bomb and remembering that he is also a generally nice human being.
Whether they do so or not, we will learn on June 22, when season 3 of 'The Umbrella Academy' premieres on Netflix.