${Fe}^{3+}:[{Ar}] 3 {~d}^{5}$

Hybridisation : ${sp}^{3} {~d}^{2}$

Magnetic nature : Paramagnetic (so this complex response to external magnetic field)

$2.$ $\left[{Ni}({CN})_{4}\right]^{2-}$

${Ni}^{2+}:[{Ar}] 3 {~d}^{8}$

Hybridisation: ${ds} {p}^{2}$

Magnetic nature : diamagnetic

$3.$ $\left[{Co}({CN})_{6}\right]^{3-}$

${Co}^{3+}:[{Ar}] 3 d^{6}$

Hybridisation : ${d}^{2} {~s} {p}^{3}$

Magnetic nature: diamagnetic

$4.$ $\left[{Ni}({CO})_{4}\right]$

${Ni}:[{Ar}] 3 {~d}^{8} 4 {~s}^{2}$

Hybridisation : ${sp}^{3}$

Magnetic nature : diamagnetic