titan (shingeki no kyojin)
The main antagonists of the manga and anime series Shingeki no Kyojin at least until the chapter and episode "The Basement", where real enemies, the Marleyan Empire, were revealed. They are giant humanoid, nearly unkillable creatures, having hunted and devoured humanity till near-extinction. Which was revealed to be a lie in the above-mentioned chapter and episode, where it was also revealed that they are in fact a race of humans called "Eldians" that can transform into a giant form at will, and thus they were oppressed and eventually isolated inside the Paradis island by the Marleyans. Who spread the lie about the Eldian's origin to have them (i.e. those inside the walled cities) eventually killed each other out.