The name Sin Heartless was created along with the internet personality to be the absolute foil of the normal people. Sin refers to the modern culture's malice, indifference, discrimination and how they result in autists' and minorities' lives to be ruined in one way or another. Heartless signifies the series of events which led to my psyche shattering and leaving me in a suicidal state for years, as well as served to make the name more edgy.
Since as an autist, me and my ideals would be cast away like carbage, I made the people in the internet hate me, despise me. I provided people in the internet something they will hate. Pretentious, cynical, edgy, insane, aggressive... A "villain" to their story. I let the hatred, pain and frustration out without any restraint.
And it worked. My confidence in RL increased drastically and people got to kick, loath and bully the internet personality. Hero and a villain to a story in the place where the people gather behind usernames and avatars.