Considering entropy (S) as a thermodynamic parameter, the criterion for the spontaneity of any process is :-

According to the second law of thermodynamics, a process is spontaneous if the total entropy of the universe increases.
$\Delta S_{total} = \Delta S_{universe} = \Delta S_{system} + \Delta S_{surroundings}$
For a spontaneous process: $\Delta S_{system} + \Delta S_{surroundings} \gt 0$. At equilibrium $\Delta S_{total} = 0$.
Entropy of the system alone or of the surroundings alone is not enough; for example, freezing of water below $0^\circ C$ is spontaneous although $\Delta S_{system}$ is negative, because $\Delta S_{surroundings}$ is larger and positive.
So the criterion is $\Delta S_{system} + \Delta S_{surroundings} \gt 0$.