Behold, the hope of him is in vain - That is, the hope of taking him is vain.
Shall not one be cast down even at the sight of him? - So formidable is his appearance, that the courage of him who would attack him is daunted, and his resolution fails. This agrees well also with the crocodile. There is perhaps scarcely any animal whose appearance would be more likely to deter one from attacking him.