Monsters. Though they are capable of unimaginable horrors, it has been proven that people can be capable of much worse. Is mankind the scariest monster of all?
What distinguishes heroes from villains when both are eerily similar? Both denote resilience, intelligence and have learned to master the fine art of deception in order to outwit their foes. Fictional characters, whether human or otherwise, have one of two options: They can merely survive or thrive in the face of adversity.
Though monsters and humans can be one and the same, what separates one from the other is the villain's encompassing desire for self-preservation and the hero's desire to preserve humanity.
Apathy is what makes a villain inhuman. Compassion is what makes a hero humane.