Berish Berger gave XX, of New Jersey, $36.5 million, believing the money would be invested in two lucrative real estate deals in Philadelphia.
But a court heard the deals were part of a scam targeting wealthy members of the Orthodox community. The Sunday Times Rich List recently estimated Mr Berger's net worth at £35 million.
Mr Berger's lawyers claimed that X forged cheques and other documents to defraud Mr Berger. In one case, X forged two cheques to look as though he had spent $27 million - on a property he did not own.
In the past few years, about a dozen Orthodox investors, mainly in North America, say they have been deceived by X.
Mr Berger's lawyer, Richard Selzer, said his client trusted X because he was recommended by respected members of the community in Lakewood, an Orthodox enclave in New Jersey.
"A rabbi from Lakewood called Mr Berger repeatedly to vouch for his trustworthiness and sagacity," Mr Seltzer said this week. "He told Mr Berger how philanthropic X was.
"X is an enormous contributor to cheders and yeshivahs in Lakewood. He buys a good reputation with stolen money."
Last Friday, a jury in US District Court, in Pennsylvania, found X guilty of fraud.
He was ordered to pay Mr Berger $23.1 million. X's estate agency, Pine Projects, was ordered to pay Mr Berger a further $6.6 million.
Ravinda Chawla, a business associate of X who was implicated in the deals, was ordered to pay Mr Berger a further $1.65 million.
The jury also punished X with $1 million in punitive damages and a further $50,000 in damages against Pine Projects.
But X's lawyer, Elizabeth Ainslie, said: "This is a seriously flawed verdict and we are considering our options."