He would break his neck against a straw.
More Italian Proverbs:
Who has no courage must have legs.Italian
Who is in fear of every leaf must not go into the wood.
Italian
Money and friendship break the arms of justice.
Italian
The fear of war is worse than war itself.
Italian
He that is good for something is the ass of the public.
Italian
He begins to grow bad who believes himself good.
Italian