Remove symmetry and break symmetry links
If you want to delete all object copies from a symmetry group and keep only the primary objects, you can remove the symmetry.
Left to right: Symmetry group in Edit mode; the symmetry group in normal state; the symmetry is removed, leaving only the primary objects.
After completing a symmetry group, you may want to make some of its elements non-symmetrical. To do this, you need to break the symmetry link of the symmetry group, turning it into a regular group of objects. You can then edit individual objects in the group.
The symmetry link is broken in the symmetry group on the left. Then, some objects are resized, and other objects are deleted (right).
To remove the symmetry from a symmetry group
You can also remove the symmetry link by clicking Object 
Symmetry Remove Symmetry.
You can also right-click a symmetry group, and click Remove Symmetry.
To break the symmetry link of a symmetry group
You can also break the symmetry link by clicking Object Symmetry Break Symmetry Link.
You can also right-click a symmetry group, and click Break Symmetry Link.