The correct order of intensity of colors of the compound is

Correct order of intensity of colours of the compounds is

${\left[{\mathrm{NiCl}}_4\right]}^{2-}>{\left[\mathrm{Ni}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{2+}>{\left[\mathrm{Ni}(\mathrm{CN}{)}_4\right]}^{2-}$

Ni is in +2 oxidation state in all complexes. The intensity of colour depends on the strength of the ligand attached with the central metal atom because more strong ligand more splitting energy, less is intensity of colour. Strength of ligand is in the order ${\mathrm{CN}}^{-}>{\mathrm{H}}_2\mathrm{O}>{\mathrm{Cl}}^{-}$.

Splitting energy order ${\left[{\mathrm{NiCl}}_4\right]}^{2-}<{\left[\mathrm{Ni}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{2+}<{\left[\mathrm{Ni}(\mathrm{CN}{)}_4\right]}^{2-}$

$\therefore$ Intensity of colour of compound

${\left[{\mathrm{NiCl}}_4\right]}^{2-}>{\left[\mathrm{Ni}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{2+}>{\left[\mathrm{Ni}(\mathrm{CN}{)}_4\right]}^{2-}$