Survival as an antagonist is hard when the world is against you

A remake of another novel I created.
Kazuki Takumi Amagiri was always a kid with a troubling life, abusive parents, poverty, being bullied at school you know the usual sob story that probably goes in a documentary for the early life of a serial killer or something. Throughout his life he's always wondered if maybe the reason world hates him was because he had the audacity to exist. But through a series of events he met his best friend and was introduced to a series of games where he found his spark of resilience to carry on in life in a character named Markus one of the main antagonists of the book.
And ten years later he's a university student, dormmates with his best friend and is just about to finish getting his degrees.
He'd also just finished playing the third installment in a his favorite video game franchise
All was going well in life, things were looking up until in one cruel twist it was over, no fanfare, no "going out with a bang", Kazuki's life just fizzled out like a candle in the wind.
Curiously though, Kazuki's story was not over as he found himself in the body of "Markus" at the start of his story.
How will this strangely ironic twist of fate change the world at large? And more importantly how will it change our main character?