Within a Collaboration stage there are three Collaboration Roles: Members, Editors, and Administrators. Typically the Administrator role is the only role that can Submit, and therefore end, the Collaboration Stage.
However, there is a configuration that would allow a non-Administrator of a Collaboration stage the ability to Submit the form. For this to happen, the below must be true:
1. 'Allow to Manage Workflow' Permission
If a user is given the 'Allow to Manage Workflow' permission, they will in essence have Super Admin rights to the workflow. The ability to manage a workflow is set for specific roles via Workflow Permissions on the Administration tab.
2. Workflow Initiator is a non-Super Admin
If the initiator of the workflow is a non-Super Admin or has a role rank equal or lesser than the Member or Editor, the Collaboration Stage Members and/or Editors that also have the 'Allow to manage workflow' permission will see the Submit button.