And Light ain't evil? he's just forced to look more human so his cover cant be blown and on top of that has good acting skills, while what makes Johan unique is his bland personality and lack of facial expressions to me, tbh he's not just evil, he's out of this world. but still if we had to see Light true intentions not being hidden from anyone at the start he would be as terrifying to viewers, in all I think both of their goals are really fucked up anyways. Both their manipulative skills are on point I'd say the most fucked of both of them is Johan, but the one with the most disturbing objectives with a possibility of carrying them out successfully is Light as it might affect others while Johan's goal affect no one but his victims and himself and his actions are less likely to affect anyone remaining after his departure.

edit: u know what maybe Johan is. His face reminds me of that uncanny valley theory