Shoot him with a bigger gun.>Mr.Freeze
Ditto.>Ras Al Ghul
Shoot him, then shoot him some more until he's in pieces.>Deathstroke
Definitely an issue, especially if caught unprepared, but Frank doesn't try to engage metas without some proper preparation, planning, and a proper assortment of arms.>shooting Bane is laughable.
How? He's just super strong, not bulletproof.