Robber flies must be a hulking menace to their smaller, weaker prey.
Robber flies are efficient, masterful predators among insects, able to pick off prey “on the wing” (i.e. in mid-flight). I would imagine they are pretty intimidating to a targeted bug — if it has time to see the robber coming!
BugPhoto.net 
Love those eyes…glad they aren’t bigger than us. I’d hate to see something like that bearing down on me. :)
You’re not kidding!