I noticed quite a few similarities between the two
They both had very tragic pasts,they both committed atrocious acts to eventually "save mankind". Their ultimate goal was to destroy humanity to end their suffering. Only difference is that Krelian atoned for his wrongs, Seymour died believing what he did was right. Unlike most villains, they don't have the "I'm gonna destroy the world because it's there" or "I will become a god" motive.