[Anthony]

Hm. Really, only the monsters with significant reproduction are good at taking over the world. There's two critters with infectious attack (horde zombie and vampire), but both have weaknesses that will probably prevent them from taking over the world.

It seems likely that all fungi, molds, slimes, and spore clouds can reproduce on corpses, though not too dangerous unless combined with something that increases mobility, such as horde zombies, and only slimes specifically say they turn corpses into more slime.

Oozes can in theory spread explosively, but the trigger for their duplication is too hard to achieve, so unless they have an additional duplication mode probably won't. A gray pudding can produce ghosts at a terrifying rate, though how much of a problem this is depends on what type of ghosts it creates.

Werewolves, oddly, do not have infectious attack.