In $SO _{4}^{2-} \Rightarrow bp =4, lp =0 $
$ \therefore$ hybridisation $sp ^{3}$
In SF $_{4} \Rightarrow bp =4, lp =1 $
$ \therefore$ hybridisation $sp ^{3} d$
In $SF _{2} \Rightarrow bp =2, lp =2 $
$\therefore$ hybridisation $sp ^{3}$
In $S _{8} \Rightarrow bp =2, lp =2 $
$ \therefore$ hybridisation $sp ^{3}$
Thus, only $SF _{4}$ does not have $sp ^{3}$ hybridisation.