Return only unique id's that are not associated with value

Hi all, I'm attempting to use two tables and do the following in query:

Return all instances where a unique rpt_id does not contain an fname entry
of 'useOnlyMostRecentScan'. This should not return rows that have
'vuln-severity' but only unique rpt_id's that cannot be associated with that
value at all. Below are the example tables, any help would be greatly
appreciated.

report_filters
rpt_id fname
951 useOnlyMostRecentScan
951 vuln-severity
932 vuln-severity
952 vuln-severity
952 useOnlyMostRecentScan
950 useOnlyMostRecentScan

reports
rpt_id rpt_name
951 Test1
951 Test1
932 Test2
952 Test3
952 Test3
950 Test4

I thought a WHERE NOT EXISTS and having statement would work but it either
returns the whole set or none of it, I'm thoroughly confused at this point.