Best done with sharpshooter, if you have serial you could wipe out the entire screen.
Lighting reflexes help out doing a free pistol shot.
With grenadier a volatile shot could wipe out a group with 3 aliens.
Bladestorm could be Ranger secret weapon against Chrysallids and Lancers.
Psi Operatives also have AOE effects.
Only Specialists dind't found a way yet.