If you are not able to access Programs & Features to remove a Windows Logon agent you can try the following.
First disable the agent following https://help.authanvil.com/hc/en-us/articles/360000099387
Next use Windows uninstaller by Microsoft: https://support.microsoft.com/en-us/help/17588/fix-problems-that-block-programs-from-being-installed-or-removed