So more from Primal because why not?
Who is the Night Feeder? What has it done?[]
The Night Feeder is an enigmatic theropod who is the main antagonist of the episode of the same name. Unlike the other dinosaurs like Fang who kill merely to survive, the Night Feeder is a serial killer in dinosaur skin. It doesn't even kill its prey for consumption: rather, it kills for sport. It first makes its presence known to Spear and Fang when it leaves the half-eaten mutilated corpse of a Smilodon for them to see. It then terrorizes a group of ceratopsians, relishing in their fear before going in for the kill.
It hunts Spear and Fang but expresses fear towards light. The duo take advantage of this and start setting the trees on fire to trap the Night Feeder. The Night Feeder tries to make a go for them one last time, but Spear impales it with a lit stick which sets the oily substance on its body ablaze.
Mitigating factors? Freudian Excuse?[]
If we are going off solely season 1 where dinosaur sapience is questionable, then I would not try making a case for the Night Feeder. However, season 2 makes it clear that dinosaurs are fully sapient creatures with their own emotions and thoughts. Take Fang for instance: she is aware of her surroundings and can choose to not be murderous or show altruism. Her partner, Red, also is shown with redeeming traits rather than just simply being a mindless predator. Or then there are Fang's second pair of kids. What I am saying is that these dinosaurs, while having to hunt, are shown to be thinking creatures who can be reasonable when it regards their interests.
The same can be said of the Night Feeder: it chooses to slaughter other dinos not out of predation but because it enjoys invoking fear into them to extend their suffering before killing them. It never even really eats its prey either. Though, of course, I am basing this just on Primal. For all intents and purposes, dinosaurs from the Jurassic Park franchise or other predators would still not count. Primal is its own thing, so I am basing that strictly on how THIS show depicts its prehistoric animals.
Who is the Mad-Man? What has he done?[]
The Mad-Man appears in the only non-prehistoric episode "The Primal Theory" which takes place in the 1800s of England.
He was an escaped mental asylum patient who had reverted back to his primal state. While the "Historical Society" was debating whether modern man could ever revert back to their beastly origins, there comes a noise from upstairs that alerts them. They discover the Mad-Man chowing down on the butler's corpse but he immediately sets his sights on them. He beats two of the Englishmen as well as ripping their throats out.
The Mad-Man proves to be a true sadist by using one of the men as a human shield and toying with the remaining men. Cornering them at the manor's fountain, he tries to drown Lord Darlington to death but apparently that wasn't good enough for his tastes. The Mad-Man instead elects to make Darlington watch as he chews chunks out of Charles (a reference to Charles Darwin because evolution).
Darlington (who I personally interpret as being Spear's descendant), becomes fully primal and fights with the Mad-Man killing him by eerily slamming a sharp wooden beam into his brain in a way not too dissimilar to Spear in the first episode.
Freudian Excuse? Mitigating factors?[]
To me the make or break on whether he is too insane to count. To me...honestly no? He is obviously an insane man, but he is still nevertheless displayed as an intelligent predator who chooses to kill his prey in viciously brutal ways like ripping out throats or drowning them. He still toys with his victims as well to really prolong their suffering. He never speaks as, besides the Historical Society, the lack of dialogue is something that is done in the show, but from his facial expressions to his mannerisms, it is clear that he does what he does because he loves it.
Heinous standard[]
Already explained a bit of the standard in Queen Ima's blog, but to reiterate: this is a very dark series with Ima standing out because she has the highest body count of the series due to forcing Spear, Fang, and Kamau to decimate several civilizations up to and including a completely pacifistic people who gave her a peace offering.
As far as dino baddies go, the Night Feeder has a high body count and stands out because Season 2 really depicts that all dinosaurs have a level of sapience to where they are not always chaotically evil/dangerous and can be reasonable and negotiable (for instance Spear having to talk Fang into going along with whatever Queen Ima wanted in order to protect her remaining two eggs).
So the Mad-Man...has a noticeably smaller body count of about 5 or 6 with two attempted. With that being said, he is just an ordinary human (I think) with no resources to speak of, but I think he does enough to be considered. Plus also being a cannibal.