Which of the following metal halides have more covalent character?

According to Fajan's rules, the covalent character of a metal halide increases with an increase in the positive charge on the central metal cation. A higher charge on the cation results in greater polarizing power, which increases the covalent character of the bond.

The oxidation states of the central metal cations in the given options are:
$\text{SnCl}_2$: $+2$
$\text{PbCl}_4$: $+4$
$\text{SbCl}_3$: $+3$
$\text{PbCl}_2$: $+2$

Since $\text{Pb}$ in $\text{PbCl}_4$ has the highest oxidation state of $+4$, the $\text{Pb}^{4+}$ ion has the maximum polarizing power. Thus, $\text{PbCl}_4$ has the most covalent character.

Answer: $\text{PbCl}_4$