Report them and hope that mods agree?

I assume you mean on some other account, because your current account seems to be empty?

Report them to their own server’s administrators. If that fails, message your own server’s administrators. If the other server is not being sufficiently moderated, your server’s admins may wish to defederate from them.

If your server’s admins don’t want to moderate the way you expect them to, you may want to switch to another server with a moderation staff that aligns more with your values.

As a last resort, you can set up your own server if none of the publicly available options suit you. This is complicated, but puts you in full control of what you will or will not see.

Report them, and then block them.