How do I remove an activity from a user account?

Select the "Activity Management" tab on the left Navigation menu.
On the Activity Management page, use the search bar to locate the desired activity you want to change the Assignment Details for.
Select the "Registrations" sub-menu and select any user whose assignment details you would like to update.
With all desired user's selected, select the 'Unassign' button on the top right of the screen.
Once the button is selected, the users will have the instance of the activity assignment removed from their account and no longer have access to the activity.

After reading this article, you will be able to remove an activity from a user's profile.