I really wish I knew how to get in contact with the author, I think the "final bosses" should be some crazy badass mercs and soldiers. Imagine if someone learned about this project, but instead of exposing it, they implanted undying bastards like Jack Churchill, Lee Christmas, Aimo Koivunen, Ernst Junger, Adrian Carton Wiart, or....
Petar Brzica
In fact, for a wild twist,
you could even double it up!
Imagine one of the "soldier implant project" heads
is none other than one of the project subjects himself!
Imagine the lethality potential of
being trained by your origin!
They are really not taking the pitch potential to its logical end.
So, so much more could be done,
and he already opened the door with Mengele!
Imagine Mengele losing his shit
and being deathly afraid upon hearing some of his most heinous colleagues, like Dirlewanger, Hojo Enryo, or Amon Goeth being on the opposing side.
He just suddenly falls to his knees crying as his serial killer friends stare in confusion.
Forget hundreds in a career, they killed hundreds by the night! Run girls, ruuuun!
Maybe introduce them doing something similar to Akumetsu's slaughter of the coup forces, 300 vs 1, or the tv studio rampage