Shape of \(\left[ NiCl _4\right]^{2-}=\) Tetrahedral

The oxidation state of \(Ni\) in the complex is \(+2\). It has outer electronic configuration of \(3 d^8\).

Since, chloride ion is a weak field ligand, there will be no electron pairing. Hence, one \(4 s\) orbital and three \(4 p\) orbitals will hybridized to overlap with four \(3 p\) orbitals of \(Cl\). This will result in tetrahedral geometry.