Maurice “Hank” Greenberg spent some of his 90th birthday party like he’s spent much of the past decade: angry.

As he addressed his family at a lunch at a private estate this month, one of his sons made another laugh. Then their sister cracked up. Greenberg told her to leave if she couldn’t keep it down.

“It got held onto for the rest of the day, so that when we were leaving he still gave me grief about it,” his daughter, Cathleen London, a 52-year-old family physician, said a day later. “I said, ‘I’m sorry.’”

Greenberg, who built American International Group Inc. into the world’s largest insurer, doesn’t let go easily. A decade after losing control of the company, he’s waging one of Wall Street’s longest and most expensive wars for redemption. That means trying to build up another insurance business while fighting claims that he’s responsible for sham transactions, suing former New York Attorney General Eliot Spitzer for defamation and taking the federal government to court, saying the 2008 bailout that rescued AIG cheated shareholders out of at least $23 billion.

Winning at least one of those fights isn’t as improbable as it once seemed. As the U.S. trial got under way last year, Credit Suisse Group AG analysts put his chances of winning at 1 in 10 and The New Yorker described him as “a dogged old coot.” The bank boosted odds to about 1 in 3 after his lawyer David Boies, who has represented Al Gore and Philip Morris, hauled Ben S. Bernanke, Henry Paulson and Timothy Geithner to the witness stand and wrapped up closing arguments last month.

‘No Idea’

Trim and fit in his Park Avenue office this month, a waist-high hourglass across from his desk, he didn’t want to answer questions about the case, his company, himself or turning 90.

“I was no different the night before, the day before, the week before, the month before,” Greenberg said.

When asked if he’s mellowed with age, he set his jaw, locked his eyes straight ahead and said the interview should end. “You have no idea the things that I’m thinking about,” he said. “All I’m going to do next and the year after that and the year after that, that’s none of your business. You’ll see it when it happens.”