In the third season we were introduced to Alice Tetch, the Mad Hatter's sister. In some unknown way, she was born with "cursed" blood. When someone comes into contact with it, his inner desires are revealed. Captain Barnes became the Enforcer, someone obsessed with justice; Lee revealed his side that is crazy about Gordon; Gordon revealed his part that likes to make people suffer.
However, in the fourth season it was understood that the vaccine was spread and the virus was eradicated. But... What if other characters used it? What do you think?