The results also pale when compared with the 70 percent median return yielded by all private equity transactions during that period, the Hamilton Lane study shows. That group includes thousands of smaller deals.

On an annualized basis, the largest deals generated a median 4 percent return, according to the Hamilton Lane study, which looked at 25 transactions from the era. The Standard and Poor’s 500 Index, by comparison, returned 7.3 percent a year from the start of 2006 through 2015.

“This crop of deals dragged down private equity returns," said Joe Baratta, global head of private equity at Blackstone Group LP. "The entire industry has become more disciplined.”

The private equity shops justified the high prices at the time by saying big and established companies could weather a possible downturn. But the post-2008 meltdown dashed that conviction, imperiling companies big and small.

KKR was the most active player, leading or joining in nine of the deals valued at more than $10 billion. Its record was mixed. Four of those transactions notched solid returns of 2.2 to 5.1 times the firm’s money. KKR co-led the highest-returning jumbo-deal, that of hospital owner HCA Holdings Inc.


$8.3 Billion Bet


But KKR also participated in four deals posting modest returns of 1.1 to 1.6 times what investors put in. Then there was the record $48 billion buyout of TXU, now called Energy Future Holdings Corp., which was the only total equity wipeout of the 19 mega-deals. The company’s 2014 bankruptcy vaporized an $8.3 billion bet led by KKR, TPG and Goldman Sachs Group Inc.

TPG had a subpar record for its seven buyouts, totaling $160 billion. On top of its Energy Future debacle, TPG suffered a loss in its purchase of casino operator Harrah’s, now Caesars Entertainment Corp., and gained nothing in participating in buying Freescale Semiconductor Ltd. In four other deals, it eked out a profit of half or less what it invested.


Most Profitable


Blackstone and Carlyle Group LP, the two biggest buyout firms, and Bain Capital distinguished themselves among the group by doing multiple deals and dodging any losses. Blackstone led the $26 billion purchase of Hilton, a deal that has morphed into the most profitable leveraged buyout ever in dollar terms -- a $10.8 billion partly realized gain as of Dec. 31, for an annualized return of about 15 percent.