>>33542993To be exact, Giratina isn't really Satan. It represents anti-matter and that's why it's world is the complete opposite of the normal pokeworld. So it's actions are completely in line with what it's about.
Kyurem might be a better fit for a Satan Pokemon, because it's an ice type and it eats humans. But yes, it probably only does that to survive and might not be malevolent itself, either.
Ylvetal would probably be closest to your description I guess, as the Pokemon of death, but that's not the same, either, because it had to be revived.