Some people argue that these lines suggest Antonio is gay: 'I am a tainted wether of the flock,/Meetest for death: the weakest kind of fruit/Drops earliest to the ground, and so let me:/You cannot be better employ'd Banio,/Than to live still, and write mine epitaph.' Act IV sc.i
There is also the fact that he remains isolated at the end of the play, when the other main chars. have had their stories completed by love. It's worth trying to yse the tone of his final exchanges with Portia/Banio.