The +4oxidation state of Sn is more stable than +2 oxidation state. Therefore, Sn²⁺ can be easily oxidized to Sn⁴⁺ and hence SnCl₂ acts as a reducing agent.
SnCl₂ + 2Cl → SnCl₄ + 2e^-

The other compound elements are in their most stable electronic state.