From [villains.fandom.com][1]:
> In an alternate reality, Batman became a ruthless anarchist after his parents are gunned down by Stalin's police force, vowing revenge on Pyotr Roslov and 20 years later became the most wanted man in the Soviet Union.

[From wikipedia][2] we learn that Pyotr Roslov was the head of the [NKVD][3]. He shoots a dissident couple (batman's parents) in front of their son (who would later become Batman) for anti-Superman propaganda.


  [1]: https://villains.fandom.com/wiki/Batman_(Red_Son)
  [2]: https://en.wikipedia.org/wiki/Superman%3A_Red_Son#Plot
  [3]: https://en.wikipedia.org/wiki/NKVD