Poly anion formation is maximum in

 catenation is a property in which atoms links with each other to form chains, occurring only among the atoms of an element that has a valence of at least two and that forms relatively strong bonds with itself.

After carbon we see that sulphur has  the maximum tendency to show catenation. Thus it forms polyanions such as ${\mathrm{S}}_3^{2-},{\mathrm{S}}_4^{2-}$ and ${\mathrm{S}}_5^{2-}$.