Which of the following complex ions has electrons that are symmetrically filled in both $t_{2g}$ and $e_{\mathit{g}}$ orbitals?

Both the  $t_{2g}$ and $e_{\mathit{g}}$ orbitals of  ${\left[{\mathrm{FeF}}_6\right]}^{3-}$ are symmetrically filled with electrons.

A weak ligand is F. The complex will therefore be high spin complex.

The outer electronic configuration of Fe(III) is $3d^5$as, which may also be represented as  $t_{2g}^3{e}_g^2$.

Thus, the correct option is C.