Icahn: The Relentless Corporate Raider

SAN FRANCISCO -- The one thing everyone can agree on about Carl Icahn: He is relentless.

It should come as no surprise then that the activist investor will do whatever it takes to force a merger between Yahoo!(YHOO Quote) and Microsoft(MSFT Quote), even though both companies have walked away from a deal.

"He's your worst nightmare," says Mark Stevens, chief executive of global marketing firm MSCO and author of King Icahn, an unauthorized biography on the larger-than-life billionaire. "He's also the smartest guy I've ever met in my life."

Icahn on Thursday informed Yahoo! that he has put together a slate of 10 candidates -- including himself -- to unseat the company's board of directors at the annual shareholders meeting July 3.

He roundly criticized Yahoo! for failing to reach a deal with Microsoft, which had put forth an offer of $47.5 billion but yanked it off the table on May 3 when the Internet giant demanded more money.

Yahoo! has defended its position, describing Icahn's characterization of the negotiations as "a significant misunderstanding of the facts about the Microsoft proposal and the diligence with which our board evaluated and responded to that proposal."

That will not be enough to placate Icahn, however, who is bent on seeing a deal go through despite the fact that Microsoft has shown no indication that it is willing to revive discussions, stating simply that it has "moved on."

He has already purchased 59 million shares and share-equivalents of Yahoo!, and has sought anti-trust clearance from the Federal Trade Commission to buy an additional $2.5 billion worth of stock.