Unless you postulate that somehow this predator needs to feed specifically on humans, then humans aren’t going to be it’s first choice of prey. Cattle would probably be it’s first targets.
I vote for raptors, the larger ones like Utahraptor or Deinonychus. Although big and deadly by human standards, they come from an ecosystem where they’re the equivalent of foxes or coyotes, and imagine how dangerous coyotes would be if humans were only three feet tall. Not that they’re invulnerable to bullets but they’re fast breeding; they lay clutches of eggs every year and if you kill 90% of them it just leaves more food for the survivors. Crow/macaw-level smart (smart enough to learn that human with gun= danger, human sans gun= lunch), adaptable, opportunistic. They wouldn’t replace humans at the top of the food chain but they would definitely be competitors. It might become impossible to raise open-range cattle or sheep, and humans would have to live behind security fences.
But once you eat the cattle and the grains, the humans will be weaker so you can go in for the kill.
I’d go for a modified honey badger or wolverine, with bullet-resistant skin (not bullet-proof, and obviously a 50 cal sniper could kill it.) Plus add the burrows in the day thing. It would hide out in fields and try to ambush farmers from its burrows, but at night it would go out and eat livestock and crops. This would cause more people to have to dedicate themselves to farming, and thus fewer people working on technology.
Plus it would be a social animal with all the intelligence and cooperation that that implies.
Actually the old D&D medusa are sort of this - the male form [cant remember what the book called them] are immune to the gaze, and was able to unstone the victim, so she would stone them and he would unstone the body after bashing it into chunks.
What about a parasite that takes over the brain of its host? It could blend into society. The host would then crave human flesh. Sort of like a zo… oh wait.
A van with “FREE CANDY” rattle-can painted on the side?
Failing that, a story to tell where if the prospective subject dies by your hand, their soul goes to a place that is way cooler than here, and they get sexy time!