Which of the following combination of ion will exhibit highest polarisation?

Fajan's rule states that the more an anion is polarized by a cation, the more covalent the nature of the ionic bond will be. The size of the cation should be small and the size of the anion should be big for maximal polarization of the anion by the cation. Additionally, anion polarization increases with cation charge.
The greatest charge, $\left({\mathrm{Ni}}^{4+}\right)$, improves the cation's ability to polarise, which in turn raises the polarisation of the ${\mathrm{Br}}^{-}$ ion.
Hence, the option B is correct