The way he could use a victim recovering from PTSD by manipulating him is amazing. But johan just could'nt manipulate tenma i mean how could he johan was only unsuccesful once that was when he could'nt prove that tenma eas a moster. I see everyone trying to be like johan i dont know why just people want to be monster inorder to prove that monster exist, the main aim of monster was to actually be the 'different' by not being a monster. Tenma is truly underrated
"They worshipped the dragon, for he had given authority to the beast, and they worshipped the beast saying, Who is like the beast, and who can fight against it?' The only thing that can defeat the beast, would be a monster more fearsome than the first.”
Series made it look like Johan was something not of this world. Ultimately they went with him being just a human. I think this anime is basically one gigantic build up but never fully exploding since Johan is just human.