4. Mr. Freeze
You probably knew this one was coming. Mr. Freeze is one of the most sympathetic villains in the history of comics (at least since his portrayal in Batman: The Animated Series anyway). He is completely devoted to his wife, and ever since the latter contracted a very rare illness, Mr. Freeze has stopped at nothing to save her. With his signature cold demeanor that manifests itself both physically and emotionally, yet also comes from a very warm place somewhere inside of him, Mr. Freeze gives off an incredible understated bittersweet presence in almost every panel he occupies. He doesn't have to yell and scream to create drama (although his freeze gun is certainly appealing), and that's why Mr. Freeze will undeniably remain one of the most well-respected, if not immediately popular, comic book villains out there.