Villains who are known for abusing children, which is a special kind of abuse.
Child-abusers range from abusive parents and crual teachers to extremely hateful child predators who have crossed the Moral Event Horizon such as pedophiles who rape prepubescent victims, child-kidnappers or even child-smugglers who sell children to the black market. Villains who swap babies at their birth for some purpose also count as child-abusers. Children who abuse younger children - typically bullies - also count.
These villains can be tragic as they might have been bullied by their fellows in their childhood and since swore revenge against every children. Neverthless, abusing children is often considered as a crual crime, as children cannot defend themselves against adults.
Many of these villains, but not all of them, have a deep hatred of children, which is purely hypocrite, as these villains were themselves children at some point, unless if they're an evil creation. Some may also hate particular children, for instance their foe's children.
By definition, child killers also count as child-abusers.
IMPORTANT: do not add villains who only aduse teenagers and/or adults on this category, since teenagers and adults are obviously not children. Also, those villains must aim for children. Villains who accidentally harmed children or do not seek to harm children in particular such as Cataclysms (unless the Cataclysm want to destroy a child-world) do not count.