Assuming CIS + PIS off... If Strange isn't worried about collateral damage and is just dedicated to taking them out... He does it with ease. For a person capable of being able to even challenge the likes of Shuma, Dormammu etc. summoning up enough energy to nuke an area doesn't seem to be much of a problem and none of these characters have the durability to handle that.
Does Strange get to channel higher beings??? If so channeling Vishanti for the win. Hell channel Agamotto alone probably do it with ease.