Welcome to Meta 
By default, users with TL2 and up can ignore other users. Admins can change that in the site settings. The setting is called Ignore allowed groups.
It’s possible to ignore users with TL4 (leader). So if you like the community apart from that person, you could try to reach TL2 to ignore them. By default, the requirements for TL2 don’t ask for too much active participation.
Have you tried to contact a staff member regarding the user? Even if they don’t think it’s necessary to intervene, they could perhaps activate the ignore function for you.