It would have to be scarecrow or joker. Joker mainly in the arkham series and animated series. Then there's scarecrow. He will be focused on the arkham series. We will start with the joker, in the arkham series he is completely insane. He injected himself with titan a more xtreme version of venom. He then dies in arkham city. Then in arkham knight [spoiler]spoilers ahead[/spoiler] He is released via fear toxin in batman deepest fear. Watch this I will be back with a link for a rather amazing performance. Scarecrow. He is rather perfectly sane except for a few exceptions.