Pedophilia is the condition of being sexually attracted to underage children, although this in itself is not necessarily "evil" the condition is reviled by society and becomes a serious crime if acted upon (via inappropriate handling of a minor) - there is also no denying a strong link with pedophilia and other sexual disorders and many pedophiles have become involved in extreme cases of child-abuse and murder, with the most vicious even engaging in torture and mind-games.
The modern world has become especially aware of the dangers of pedophilia but the phenomena is as old as humanity itself and cases of child-murder, molestation and worse have been documented since the beginning of time.