What chareristic is most shared by most simple polyomatic ions

They are anions.

The characteristic that is most shared by most simple polyomatic ions is that most of them are anions

In chemistry polyatomic ions are those ions that contain 2 or more different atoms which are chemically bonded to each other. Polyatomic ions may be both positively charged or negatively charged. But mostly if we take a look at the polyatomic ions, we will see that almost all of them are anions .

Some examples of polyatomic ions are given below.