I have recently had a user leave my organisation. I have successfully removed their Adobe Analytics Account, Target Classic Account and Enterprise Dashboard account, however they still appear in my list of users for Target Standard and there doesn't appear to be an obvious delete button like there is for all of the other tools.
Generally To remove a user from Enterprise dashboard we Login to Marketing Cloud------>Adminstration--->>Enterprise Dashboard----> Products--->Adobe Target----->Select Target product group to which user belongs ---->Select user to delete .
and the user is deleted . If you have done the same process Please logout from your Adobe Marketing cloud account and login again to Adobe Target and check to see if user is still show in the user's list for Adobe Target standard.
If the problem still persists . Please do let us know we will further debug the issue at our end.
I have this issue as well, when I delete someone from Marketing Cloud Admin they are never removed from the users list in Target, I just assume their access has been revoked and it's just one of the many bugs in the system!