the process was pretty hardcore: first was the gladitorial/olympic games that only few survived.
second was the the grueling tests that were 1) having your dna strands intermingled with korban empire's most dangerous animals supposedly extremely painful, and 2) getting shown extremely violent and mind bending visions till you died of shock and insanity.
the third was getting fitted with a cybernetic overhaul, this is where all but bill perished.
the korbanites wanted vengeance that badly, and why bill goes all in on anyone he fights.