Warning! Spoilers for Crime Syndicate #1 below
Earth-3 might be home to the evilest Superman, but a flashback reveals that the Kents are responsible for corrupting him. This suggests that this version of Clark Kent, along with everyone else on this planet, aren't just ambivalently evil just because it's "a world where everything we know is turned upside down...and where good does not always triumph in the end." Certain events made them this way, and, unfortunately for Clark of Earth-3, Ma and Pa are responsible.
When presenting Clark of Earth-3's origin flashback, writer Andy Schmidt provides access to Clark's thoughts, which prove that he wasn't always necessarily destined to become the evil version of Superman in Crime Syndicate #1 drawn by Bryan Hitch. Even though the Kents took advantage of Clark's powers by making him do all of their work while instilling fear of the outside world in him, the boy grew up loving his parents and viewed them as the only people in the world he could trust.
It's only later when Clark realizes that his parents, Jon and Martha Kent, were clearly using him that an uncontrollable rage consumes him, beginning Clark's journey to becoming the antihero known as Ultraman. Readers see this almost immediately when an angered Clark adopts the same negative language the Kents used to instill fear in him of becoming a person who takes advantage of others' generosity without giving anything in return: "You ain't nothing but a couple of freeloaders."
In the present day before ing the evil Justice League, Ultraman later espouses a rather alarmingly perverse view of Metropolis and humanity as a whole, which he expresses clearly when a tentacled alien creature threatens to take the city away from him: "Metropolis is mine...or nobody's." What happened to Clark on the night he learned the truth of himself clearly shaped his belief that humanity is something that he can possess. Because of how his parents treated him, he now views humanity as nothing but freeloaders who will use his great powers - powers that him better than everyone on Earth. As he said as a child to his parents: "You think I owe you? I should be grateful? For what? What could a couple of humans possibly do for someone like me?" It's because Ma and Pa showed him that mankind isn't worthy of his love or respect that he now views them as things that are lesser than him and objects he can own.
The real tragedy is that what Ultraman experiences isn't necessarily proprietary to Earth-3. Clark of Earth-3 began as the same positive, wonderful boy as his counterpart on New Earth. It was the disgusting nature of Earth-3's Kents that shaped him into the abomination he would later become. This suggests the same could have happened to Superman on New Earth. Luckily for this Clark, that monumental moment when he learned of his true origins didn't mold him into a monster. That's because the Kents of New Earth treated him well. Due to their unwavering love and respect for him, Superman came to view humanity as a race that deserved protection and that was capable of achieving true greatness.
