remove the "scan with sophos anti-virus" finder menu command

I too have this issue now in the year 2017, as OP was from 2012.

Whe had Sophos Anti-Virus on Mac OS 10.7, after upgrade directly to Mac OS 10.12 (Sierra) Sophos Anti-Virus was incompatible software. We still have the context menu option "Scan with Sophos Anti-Virus", but strange enough only for the main user. A new user does not have it. There is no "/Library/Contextual Menu Items/Sophos Anti-Virus.plugin" nowhere (except it hides itself for protection reason and I can't get at it). I did run the (old) "Remove Sophos Anti-Virus".

When I install the current Sophos Anti-Virus, the context menu item in question is correctly replaced with "Services", but when I de-install Sophos Anti-Virus again (to verify), the context menu "Scan with Sophos Anti-Virus" re-appears. Any and all searches for 'sophos' or for the text ("Jetzt mit Sophos Anti-Virus scannen") do not show any results.

What else can be done to remove the old, outdated "Scan with Sophos Anti-Virus" definitely?

If you're simply trying to get rid of multiple listings for Sophos when you right-click on an item and get Services, open System Preferences>Keyboard>Shortcuts, pick Services from the list on the left and scroll down the right side window until you reach the Sophos listings. There will probably be more than one checked. Unchecking all but the one that works (test the Services Menu listing to ensure you've left the correct one checked) should solve the problem.

If you're simply trying to get rid of multiple listings for Sophos when you right-click on an item and get Services, open System Preferences>Keyboard>Shortcuts, pick Services from the list on the left and scroll down the right side window until you reach the Sophos listings. There will probably be more than one checked. Unchecking all but the one that works (test the Services Menu listing to ensure you've left the correct one checked) should solve the problem.