Cherico....
Nowhere in the story are we ever told why Shylock had such a huge grudge against Antonio. And was Antonio an "asshole" for borrowing money in order to lend it to a friend? Foolish, sure. The Book of Proverbs has clear warnings against standing surety for loans. It was not Antonio's fault that all three of his overseas trading ventures failed, when presumably one alone of his ships returning safely to Venice would have put him back in liquidity enough to repay the debt, no problem.
Also, Shylock was repeatedly offered repayment of the loan at 300% of the principal. But no, he wanted to cut someone's chest open instead.
Antionio and shylock had history Antinio was an outspoken anti semite, at first Shylock didnt want to lend Antionio money because the man had been an utter ass to him and because he under cut his business model when ever possible so yeah lots of bad history there. Then his daughter elopes with some rando steals his shit and on top of that takes a ring that is one of the few things he had left of his dead wife.
And Antionios ships are left at sea and Antionio has every motive and a history of fucking with Shylock, and with his community and Shylock after a life time of being fucked over says no.
No not this time, this time I'm getting some fucking pay back, and Antionio isnt blameless in this and knows it. The contract didnt involve interest, and at the time he considered the terms fair. If Portia had minded her own god damned business because she doesnt have the legal training to be a judge or lawyer or juridiction to the case. Antionio would have lost a pound of flesh.
It would have hurt like a bitch, but he would have probally survived with a nasty scar, and a story and Shylock would have gotten his revenge.