‘ . . . How like a fawning publican he looks!
I hate him for he is a Christian,
But more for that in low simplicity
He lends out money gratis and brings down
The rate of usance here with us in Venice.
If I can catch him once upon the hip,
I will feed fat the ancient grudge I bear him.
He hates our sacred nation, and he rails,
Even there where merchants most do congregate,
On me, my bargains and my well-won thrift,
Which he calls “interest.” Cursèd be my tribe
If I forgive him! (A I, s iii)

Shylock explains his enmity for Antonio. He has a bias against Antonio as a Christian and hates him even more for Antonio’s practice of lending money without interest, undermining Shylock’s usury business. Shylock wants revenge for years of Antonio's mistreatment. Antonio hates people of the Jewish faith and always speaks badly about Shylock’s merchant deals. Readers may note the irony of Shylock hating Antonio because of his Christianity, but seeking revenge because Antonio discriminates against his Judaism. Clearly, hatred and religious division spark the fire of revenge.

I am bid forth to supper, Jessica.
There are my keys.—But wherefore should I go?
I am not bid for love. They flatter me.
But yet I’ll go in hate to feed upon
The prodigal Christian. (A II, s v)

Shylock explains to his daughter Jessica his suspicions that Bassanio and Antonio only invited him to dinner because they want something from him. He chooses to attend in order to exploit Antonio’s liberal hospitality. Shylock reveals a twisted vengeful character in his choice of words to “feed upon” Antonio, foreshadowing the pound of flesh he’ll demand.

Never did I know
A creature that did bear the shape of man
So keen and greedy to confound a man.
He plies the duke at morning and at night,
And doth impeach the freedom of the state
If they deny him justice. Twenty merchants,
The duke himself, and the magnificoes
Of greatest port have all persuaded with him.
But none can drive him from the envious plea
Of forfeiture, of justice, and his bond. (A III, s ii)

Solanio discusses with Bassanio Shylock’s aggressive intent to get revenge on Antonio. He explains that Shylock would rather take Antonio’s flesh than money to pay his debt because such an act would give him the revenge he has always wanted. Solanio also voices concern as he believes no one can stop Shylock or deter him from his need for revenge. While Shylock believes he has valid reasons for his hatred of Antonio, his hatred and revenge take over his character and blind him.