Bizarro is a monstrous supervillain from DC comics, appearing in multiple works primarily as an enemy of Superman, though sometimes he is depicted as an antihero and thus can vary between an opponent or unstable "ally" of many heroes.
Bizarro is depicted as an imperfect clone of Superman who is reversed in mannerism and abilities, for example he has fire-breath, freezing-vision and often believes the opposite of what he says (calling enemies "friends" and calling "good" "bad" etc).
Inspirations outside of comics for Bizarro are clearly creatures such as Frankenstein's Monster.