Overall, our study of Fe(II) SCO complexes with a variety of DFAs highlights that caution must be exercised while using DFT to study SCO complexes because the predictions depend strongly on the functional, with the amount of HF exchange and parametrization of the functional playing a crucial role. Moreover, accurate prediction of SCO behavior, e.g., by predicting experimental T1/2 values curated in our SCO-95 set, presents an outstanding challenge for the development of both more sophisticated modeling protocols to incorporate packing effects as well as for developing improved wavefunction theory and DFT energies to predict single-step SCO.