Since I cannot see your list, I have to make this part up a little.
1. I am assuming you have a field that has the emails, but another field that tells you what they are? Level 1 2 3 4 whatever?
If that is the case you can write an odata filter to essentially say
ColumnName ne 'Leader1Value' and ColumnName ne 'Leader2Value' and ColumnName ne 'Leader3Value' and ColumnName ne 'Leader4Value'
Now it won't pull back any emails where your Identifier (not the email address) that tells you what they are (persona wise) is any of those 4 values.
Now if you are saying you ONLY know them by email address, that is not a great way, but then you would make the ColumnName the email and you would do ne 'emailaddressfield' and you may want to wrap it into toLower(emailaddressfield) depending on how you store the email address, all caps, mixed etc.
Or you can use a Filter Array and essentially you would write the same stuff above but in a different format in advanced mode in the FilterArray, which is actually more a pain imho then filtering them at the Get Items level.
If these suggestions help resolve your issue, Please consider Marking the answer as such and also maybe a like.
Thank you!
Sincerely, Michael Gernaey