Why does oxygen show negative oxidation state,whereas other elements of group 16 show positive oxidation state????????

Due to its high electro-negativity(second most electronegative element after Fluorine), oxygen indicates negative oxidation state and does not demonstrate any positive oxidation state, aside from in OF2 and O2F2. Remaining elements of the group, show positive oxidation states due to the availability of d-orbitals in their particles.