Deactivate a User
Lock a user out of the management interface and all spaces.

Click Users.

Select the user User Sidebar Item you want to deactivate.

Click Deactivate User.

WARNING

Deactivating a user will not remove them from any groups or spaces they're a part of. As soon as you reactivate them, they will be able to access the same spaces they could access before.

TIP

There is no way to permanently delete a user, and there never will be.