Audiences watching The Iceman, a new film about real-life hitman Richard Kuklinski who killed more than 100 people, may come away with the uncomfortable feeling that they have been rooting for the bad guy.

Every time I look at Kuklinski I see the little boy that he once was and I imagine how much fear and pain he had to endure as a child

Israel-born director Ariel Vromen sets out to paint a rounded picture of the notorious mob enforcer, who died in jail in 2006, portraying him not only as a cold-blooded killer but also a charming, devoted husband and father of two girls.

The Iceman had its world premiere on Thursday at the Venice film festival. Although not in the main competition the film has earned glowing early reviews, in particular for lead actor Michael Shannon playing Mr Kuklinski.

The towering American, as physically imposing as the man he portrays, is both tender and cruel.

The Hollywood Reporter said: “Once again he can explore the darkness within like few actors working today.

“It’s a tribute to this astonishing actor that no matter how vicious his actions, Richie remains an anti-hero with an unyielding grip on our attentions.”

The 38-year-old earned an Oscar nomination for his portrayal of John Givings in Revolutionary Road and with the Venice festival coming at the start of the awards season, he could figure again this year in the lead actor category.

“By the end of the movie, you’re like, ‘I like that guy!’ and you’re like, ‘why?’ And I think those connections make it different than many other gangster films,” Vromen told reporters after a media screening.

Shannon, loudly cheered at the press briefing in Venice, said he sought to understand how Kuklinski became what he did.

“Every time I look at Kuklinski, I see the little boy that he once was and I imagine how much fear and pain he had to endure as a child and the whole process of his personality forming,” Shannon said.

The movie contains scenes of Kuklinski as a boy being savagely beaten by his father.

“I also saw someone who was filled with a lot of self-loathing,” Shannon added.

“He really didn’t think he could do anything else, he didn’t think he had any talents, he didn’t think he was intelligent. He thought the one thing that he did have in excess was rage.”

Kuklinski died in the prison wing of St Francis hospital in Trenton, New Jersey, aged 70.

He became known as the “Iceman” because he sometimes froze the corpses of his victims in order to disguise from police the time of death and was not shy in boasting of his exploits, including in HBO documentaries about him.

The 6 feet 5 inch man was reported to have told lies to exaggerate his crimes but in 1988 he appeared in a New Jersey court and was convicted of five murders for which he was serving consecutive life sentences when he died.

Winona Ryder plays his wife Deborah, Ray Liotta is his employer-turned-rival, Mafia boss Roy Demeo, and David Schwimmer, best known as Ross in the hit TV series Friends, is the small-time hustler Josh.

Ryder said she avoided researching the role of Kuklinski’s wife in order to better convey the uncertainty over whether or not she actually knew the extent of her husband’s crimes.

Theactress added that she was drawn to the project in part because she admired Shannon.

“I think I’ve gotten to a place in my life where I just want to have a good life and so a film has to be pretty great for me to want to leave my life to go and spend this time making it.”

Vromen said the only contact he had had with people portrayed in the movie was with Kuklinski’s older daughter, who was a Facebook friend.