Hi,
You can use a segment for this. At the tab where you select your lists you will find this option at the bottom of the tab. Slect Yes, click save & continue and you will see an extra tab where you can define a filter to exclude that user.
This filter ias ad hoc. If you want to use the same filter regularly you can define a new segment in Acymailing->Segments. It's documented here: https://docs.acymailing.com/main-pages/campaigns/segment
