Electrophile is a species that forms bonds with nucleophiles by accepting an electron pair, because electrophiles accept electrons, they are Lewis acids.
$\mathrm{CN}^{-}$is nucleophile, which is electron rich in nature and electrophile is electron deficient in nature and contain positive charge.
$\mathrm{BF}_3=$ Neutral electrophile or Lewis acid (electron deficient)
$\mathrm{NO}_2^{+}=$Electrophile
$\mathrm{AlCl}_3=$ Electrophile (electron deficient)
Hence, only $\mathrm{CN}^{-}$is not an electrophile.