9. Klarion The Witch-Boy
Despite resembling a young boy, Klarion is actually an ancient sorcerer and occultist, bound to Earth by a curse, who delights in causing chaos for the heroes of DC.
Originally introduced as a magical enemy for the Demon Etrigan in 1973 by Jack 'The King' Kirby, Klarion has used his black magic, supernatural prowess, and penchant for trickery to take on the Justice League, Doctor Fate, Wonder Woman, and more.
Aided by his familiar, a cat named Teekl, Klarion has learned how to manipulate space and time, cross dimensions, summon the dead, cast illusions, and annoy everyone with his childlike approach to world domination. Unable to survive without his precious Teekl, heroes have used the familiar to defeat him, call him off, or send him away to sulk in another dimension.
Klarion has made notable appearances in The New Batman Adventures animated series, as well as Young Justice and Justice League Action - usually depicting him tricking and trapping the world's greatest heroes, turning them into kids, or trying to take over the world with his black magic.
Regardless of where he appears, Klarion exists as a powerful nuisance for whoever he crosses paths with.