The only thing is that most of his actions took place offscreen, nameley his abuse of his son, and that killing the hero isn't heinous enough either. His plan to freeze over the Unova region, while bad, doesn't really prove he's monstrous. The video game doesn't even say that his plan would lead to the deaths of millions of people. It's only fridge horror, which is something that a complete monster cannot have. Again, he is not a complete monster. Don't add him again.
You keep adding the Complete Monster category to villains who don't qualify. When others remove the catgory and explain why they don't qualify, you've been ignoring them and re-adding it. This needs to stop.
Fine I apoligize for doing that, I knew Hyperion as a tragic villain. Losing his Wife and kids to illness and feeling vengeful against the gods. Maybe he has a little honor even if he does not show it. And Galt is a bad egg (I personally consider him a complete monster) he is not as bad as Zaysen or Tint. Those two were gruesomly brutal.