Dozens of the world's wealthiest lost billions in recent months, but these 10 distinguish themselves for some of the biggest flops. It was a dreadful year for the world's wealthiest as markets and currencies around the world tumbled. More than 300 of the 1,125 billionaires we tallied on our annual list last March have since lost at least $1 billion; several dozen lost more than $5 billion. The 10 richest from our 2008 rankings dropped some $150 billion of wealth, dragged down by steel tycoon Lakshmi Mittal, estranged brothers Mukesh and Anil Ambani and property baron K.P. Singh, who together dropped $100 billion. America's 25 biggest billionaire losers of 2008 lost a combined $167 billion. More from Forbes.com: In Pictures: Billionaire Blowups, 2008 In Pictures: America's 25 Biggest Billionaire Losers In Pictures: The Biggest CEO Firings of 2008 But even in such an awful year, the stories of a few billionaires and now former billionaires stand out as particularly dreadful. Take David Ross, one of the U.K.'s most successful entrepreneurs. Earlier this month, Ross notified four public companies in which he was a major shareholder and director that he had borrowed against his shares to fund real estate investments that had soured. He will likely have to sell some of those stakes to pay off his debts. So far he has resigned from three of the four boards and stepped down from his post as an Olympics adviser. His fortune, which we estimated at $1.4 billion in March, is now worth about $150 million. Bjorgolfur Gudmundsson, former chairman and a large shareholder in Landsbanki, Iceland's second largest bank, saw the firm seized in October as the worst of the credit crisis tore through the island nation. The failure wiped out his $1.1 billion fortune. He has since had to put his holding company, Hansa, into voluntary liquidation and is selling his U.K. soccer team, West Ham. Russians were some of the biggest losers in the past year. Vladimir Lisin's Novolipetsk Iron and Steel is down three-fourths since its June peak. Dmitry Rybolovlev's fertilizer company, Uralkali, has fallen 90% since it peaked around the same time. But those losses pale compared with the troubles facing Oleg Deripaska. In March he was the world's ninth richest person and Russia's richest man, with a fortune we estimated to be worth $28 billion. Since then Deripaska has been forced to sell shares in Canadian carmaker Magna International and German construction firm Hotchief, and had to borrow $4.5 billion from a state-controlled bank to hold on to his stake in Norilsk Nickel. He will likely sell off additional assets to avoid losing even more of his fortune, now estimated at $10 billion. Or less. The biggest loser of all was Anil Ambani. Touted on the cover of our 2008 billionaires issue for having added $24 billion to his fortune in one year, Ambani has dropped $30 billion since then. But don't worry too much. His Reliance Entertainment is investing $500 million in a new studio venture with Steven Spielberg's DreamWorks. Plus, he remains quite wealthy, worth $12 billion That's something many others can't claim. In Pictures: Billionaire Blowups, 2008 1. Anil Ambani March net worth: $42 billion Current net worth: $12 billion © AP Photo Oleg Deripaska The biggest billionaire gainer last March is now the year's biggest loser. Ambani lost $30 billion in the past nine months, more than anyone in the world. Stock of his telecom company dropped after his estranged brother helped scuttle a deal with African telecom MTN. It's quite an achievement in a year in which three of his fellow countrymen--estranged brother Mukesh, steel tycoon Lakshmi Mittal and Indian KP Singh, all of whom ranked earlier among the world's 10 richest--lost more than $20 billion apiece. 2. Oleg Deripaska March net worth: $28 billion Current net worth: less than $10 billion Former metals trader survived Russia's gangster wars but may not withstand collapsing markets and heavy debts of at least $14 billion. Russia's one-time richest man recently received a $4.5 billion loan from a state-controlled bank in order to keep his 25% stake in Norilsk Nickel, which faced a margin call by Western banks from which he had borrowed. Other margin calls forced him to divest a $1.5 billion stake in Canadian carmaker Magna International and a $500 million stake in German construction company Hotchief. He's also selling stake in insurance company Inogsstrakh. More from Yahoo! Finance: Lose Confidence in Your Bank? Turn to the Web States in Worst Budget Trouble The Six Best Budgeting Sites -------------------------------------------------------------------------------- Visit the Banking & Budgeting Center 3. Anurag Dikshit March net worth: $1.6 billion Current net worth: $1 billion Dikshit designed the software for PartyGaming's successful PartyPoker game, which allowed live gambling over the Web. He left the company and sold a chunk of shares in 2006, the year the U.S. government banned gaming. He recently pleaded guilty to violating U.S. gaming laws and agreed to forfeit $300 million. He could face up to two years in jail but apparently won't be sentenced until 2010. He has already paid $100 million of his fine and will pay the rest in two installments next year. © Carl de Souza/AFP/Getty Images Bjorgflur Gudmundsson 4. Bjorgflur Gudmundsson March net worth: $1.1 billion Current net worth: zero The October collapse and government seizure of Iceland's second largest bank wiped out the $1.1 billion fortune of Gudmundsson, the bank's chairman and biggest shareholder, along with his son Thor. His holding company, Hansa, has since gone into voluntary liquidation and is looking for a buyer for its U.K. soccer team, West Ham. It's not the first time he's run into trouble. A former shipping executive, he was charged with fraud and embezzlement in relation to the firm's 1985 collapse, and was eventually found guilty on five minor counts and sentenced to 12 months' probation. 5. Luis Portillo March net worth: $1.2 billion Current net worth: $15 million Spain's short-lived real estate gold rush left one of its most visible speculators holding a nearly empty bag. Portillo--who acquired real estate firm Inmocaral three years ago, then led the takeover of the larger Inmobiliaria Colonial in 2006--personally borrowed a reported $1.4 billion from more than a dozen banks during boom times, using his stock as collateral. He resigned as chairman in December 2007 and then tried to sell his stake to a Dubai fund earlier this year. When the deal fell through, he had to sell most of shares to pay debts. Click here for the full list of the Billionaire Blowups of 2008.