If you want to delete a person in Pipeline, you can delete that person from the person's profile page or a People list view.

From a Person profile page

From the person profile page select Actions > Delete. Confirm the deletion to remove this person from Pipeline.

 From a People list view

To delete a person in Pipeline from the People list view, check the box next to the person’s name and select More > Delete (single or bulk delete).

NOTE: The ability to delete is a permission set by your account admin. Please contact an admin on your account for this permission.