Carbon-halogen bond is strongest among the following 

When the atomic size between bonded atoms are similar, then there is a strong overlapping between the orbitals and bond becomes stronger. But as the atomic size of any one of the bonded atom increases, then gradually the effective overlapping between the bonded orbitals decreases which results in low bond dissociation energy.

The carbon-halogen bond length increases due to the increase in atomic size from fluorine to astatine, thus the bond dissociation strength decreases.

${\mathrm{CH}}_3\mathrm{F} > {\mathrm{CH}}_3\mathrm{Cl} > {\mathrm{CH}}_3\mathrm{Br} > {\mathrm{CH}}_3\mathrm{I}$