Humans are made out to be peaceful when compared to alien races but this would be far from the truth. Humans are hyper aggressive and hyper sensitive to "differences". Humans fight each other over slight differences in skin color or technicalities in their religious beliefs. When "Jaws" came out, the thought of a fictional animal attacking fictional people, caused people to start killing many more sharks. Just the thought of something killing humans (besides us) triggers our swarm and destroy instincts. If something is not bullet proof, doesn't have billions, or doesn't have massive tech advantage, it is getting swarmed.
Conan with morals on is the same as bloodlusted against these guys. Since they are stupidly using melee weapons they get stomped because he is a master. Chucky, Mike and Jason are too slow and get cut to pieces. Zsasz seems like he would have a chance but he has a knife and Conan has a sword. He doesn't need that advantage.