The type of hybridization present on central atom is ${\left[\mathrm{Ni}{\left(\mathrm{CN}\right)}_4\right]}^{2-}$is 

Nickel has an atomic number of 28. Nickel’s electrical arrangement is Ni=[Ar]3d⁸4s².

There is a Ni²⁺ ion in ${\left[\mathrm{N}(\mathrm{CN}{)}_4\right]}^{-2}$ with the electrical configuration 3d⁸4s⁰ in the valence shell.

All electrons are coupled up in the presence of strong CN^- ligand. Complex has square planar geometry, where the vacant 3d, 3s, and two 4p orbitals undergo dsp² hybridization to form bonds with CN^- ligands. It’s a low-spin inner orbital complex