You're going about this the wrong way. Posting in the forums won't get anything done. It's not going to be seen by anyone in a position to do anything about the situation.
If this individual is as bad as you claim they are, each of you that have been targeted by this individual need to take all the evidence collectively accumulated and go to your local law enforcement agencies to file complaints. On the off chance your local law enforcement is not the correct agency, they should refer you to the one that is.
In the US, the FBI oversees the Internet Crime Complaint Center. While they only investigate certain types of crimes happening online, they do track reports for all types and will also refer reports they get to the appropriate agency for investigation. If you feel uncomfortable going directly to your local law enforcement (usually the correct agency for most US states for cyber harassment/bullying), you can file a report here:
https://www.ic3.gov
If anyone that has been targeted is a minor child in the US, they (or their parents)
need to file a report here:
https://www.missingkids.org/gethelpnow/cybertipline
(National Center for Missing and Exploited Children). These situations get taken far more seriously when a child is directly involved.
You may also want to contact legal aid organizations that offer free consultations to see if this is something that could be pursued at a civil law level against this individual if law enforcement won't consider it worth their time for criminal investigation (and perhaps even if law enforcement does take it up at a criminal level).
Anything that SE does is going to be temporary at best. As should be apparent by now, they cannot stop this individual from setting up new accounts if they're intent on continuing the harassment. Banning their account will give you maybe an hour's relief before they're back online again to continue using the new account.
SE also have no ability to control what this individual does outside of the game, such as posting lewd/suggestive images on Discord. If there is nothing that comes up in their game logs that clearly shows inappropriate activity, they will not take action
unless they are instructed to do so by a court order.
Take it to law enforcement. This is not a problem that SE will be able to fix to your satisfaction if the harassing material is being distributed outside of game and not being linked in game chat channels. A player simply being in the same place as your characters is not a violation of the ToS regardless of whether you think they have reason to be there or not.