Are you possibly using Sync to sync the logins ?

Did you try to remove this login from Lockwise (about:logins) ?

I removed it from Lockwise, but it still pulls up the entry when logging in.

If it is removed from Lockwise then you can only see data filled from saved form data.

Do you have a keyboard with a Delete key ?

You can use these steps to remove saved items from an autocomplete drop-down list.

1. click the (empty) input field on the web page to open the drop-down list
2. highlight an entry in the drop-down list with cursor Down key
   do not click the mouse or press the Enter key
3. press Shift+Delete to delete the highlighted entry

Note that hovering with the mouse doesn't work, you need to use the keyboard