I don't think this has anything to do with deleting a filter. I think they are looking for a JQL that filters out not only a specific epic, but it's children as well.
If I had to do it, the JQL would look like:
issuekey not in (EPC-123) AND ("Epic Link" not in (EPC-123) or or "Epic Link" is EMPTY)
where EPC-123 is the issue key to your epic.
Use an "AND" to join this to the rest of your epic, and you should be good to filter out Epics and issue from your query. If you need to further filter out subtasks of issues belonging to that epic, things get complicated. If you are on Server, I'm not sure if it's possible without an App, to be honest.
HOWEVER, If you are on Cloud, you can use
issuekey not in (EPC-123) and parentEpic not in (EPC-123)
To get the desired results, subtasks and all.
Hi @Sara Creenan (M&T) ,
also, check out these resources