what are the challenges antonio have faced

Antonio is a Christian merchant of Venice, he agrees to vouch for a loan to Bassanio from Shylock by putting a pound of his flesh up as collateral. Antonio of course has the challenge of delivering on something that he doesn't have. He vouches for his friend only on the expectation of his ships coming in. He faces the humiliation of forfeiting on the loan as well as loosing a literal pound of flesh. As well Antonio represents Christian charity but weakness as well. Antonio is deeply sad and unable to express this melancholy to Bassanio. Many critics feel that Antonio has an affection for his friend that is homo-erotic in nature. Antonio must keep these feelings hidden even at the end of the play.

Here is the main problem anotonio faces that is conveyed in his letter to bassanio.

•in the letter, Antonio writes that all of his ships are lost, and that Shylock plans to collect his pound of flesh. The news provokes a fit of guilt in Bassanio, which in turn prompts Portia to offer to pay twenty times the sum. ... Portia urges her husband to rush to his friend's aid, and Bassanio leaves for Venice.

• remember that Shylock wanted Antonio's pound of flesh