In season 1 (current)
the two vying for antagonist position, neither fall into that reasonable motivations category.
Contender 1 - is a giant kaiju-snail who acts more like a force of nature, destroying towns in its path and transforming other lifeforms into monsters. Other lifeforms it cant infect it will consume (the mcs being immune to infection).
It emerged from Evan (Mc's) puke after he threw up while hearing an eerie HUM broadcast over his hometown on April 5th.Evan discovers that he can crystallize offspring from this Giant Snail via touch, and believes he can do the same to this giant snail. Not evil by coice, by instinct, low intellegence & just tryng to survive
Contender 2 - Irredeamable since the 1st episode! At the moment this guy remains anonymous (seen in 1st person while the protagonist goes into a dream-like state). His handcuffs and attire hint that he might be from a high-security prision . He's someone casually kills others in his path while remaining pleasant. He enjoys testing the limits of his bizarre condition on hapless civillians he encounters. (developed a bizarre condition similar to the MC via the Hum on Apr 5th)