In which of the following compounds, sulphur exhibits least oxidation state

There are two S atoms in ${\text{Na}}_{\text{2}}{\text{S}}_{\text{2}}{\text{O}}_{\text{3}}$, one occupies central position and another present at the terminal position. S present at central position has an oxidation state, +6 but the one present at terminal position exists in -2 oxidation state.