A substance's boiling point depends on the strength of the intermolecular forces its molecules exhibit.
The stronger the intermolecular forces, the higher the boiling point. Likewise, the weaker the intermolecular bonds, the lower the boiling point.
Right from the get-go, krypton,
This leaves you with sulfur dichloride,
This time, you're dealing with a polar molecule. The two lone pairs of electrons present on the sulfur atom (not visible in the above image) and the polar
This implies that the molecule can exhibit dipole-dipole interactions, which are considerably stronger than London dispersion forces.
As a result, sulfur dichloride will have the highest boiling point of the group.