Remove old user from Remote Login permissions list On OS X 10.8 I deleted a user account which had Remote Login permissions.  Now, in the Sharing tab of System Preferences, that user shows up as "Unknown User", and clicking the minus button won't remove it.
Found the solution here, hope this helps.

1) First remove all users that can be removed from GUI In System Preferences -> Sharing -> Remote login

2) Run the below command which shows the configuration of users who have remote login access

sudo dscl  . -read /Groups/com.apple.access_ssh


example result:

AppleMetaNodeLocation: /Local/Default
GeneratedUID: 2F60778C-0931-47A4-B656-DBE07ACD843F
GroupMembers: **3D7C31B1-DEDE-4A5A-AAA8-CDD55645DC75**
GroupMembership: youraccoutname
PrimaryGroupID: 404
RealName:
Remote Login ACL
RecordName: com.apple.access_ssh
RecordType: dsRecTypeStandard:Groups


3) remove the group GroupMembers that the user(Unknown User) is in

sudo dscl  . delete /Groups/com.apple.access_ssh GroupMembers 3D7C31B1-DEDE-4A5A-AAA8-CDD55645DC75


4) Go to System preferences and see the result