Reinhold Messner and Max von Kienlin
Mountaineers
Friends Forever! Messner was a wreck after his 1970 traverse of Pakistan's 26,660-foot Nanga Parbat, during which he lost seven toes to frostbite and his brother, Günther, died, apparently in an avalanche. When expedition mate von Kienlin invited him to spend time recovering in the Munich, Germany, castle he shared with his wife, Ursula, Messner gratefully accepted.
Oops: Messner was a terrible houseguest—and not because he drank milk straight from the carton. Within a year, Ursula announced that she was leaving Max to marry Reinhold. (She and Messner divorced in 1977.) Tensions flared again in 2001, when Messner publicly blamed his old teammates for failing to help him save Günther. Von Kienlin fired back with a book, The Traverse, claiming that Messner had once admitted to abandoning his brother on the mountain. Messner scoffed in response—"He lost his wife to me," he later told Outside—but sued von Kienlin, who was ordered to revise future editions of his book.
Is Forgiveness an Option? Unlikely. Von Kienlin is willing to talk but not, apparently, to stop with the potshots. "Messner is happy about the controversy—it brings him publicity," he says. "But my dream is for all of us to stand on top of Ecuador's Mount Chimborazo and shake hands." Says Messner: "Von Kienlin is of zero interest for me."

Lance Armstrong and Greg LeMond
Tour de France Champions
Friends Forever! Cycling's once and future all-stars were dripping with mutual affection after Armstrong's first Tour de France victory, in 1999. "That performance made up for last year's disgrace," LeMond told reporters, referring to the scandal-rocked 1998 Tour. For his part, Armstrong said he considered his colleague a hero: Watching LeMond win in 1989 was "the first time I thought and dreamed about the Tour de France," he said.
Oops: With Armstrong draped in yellow in 2001—and about to tie LeMond's American record of three Tour wins—LeMond wasted no time in bashing him. Following reports that the Texan had ties to an Italian doctor then accused of assisting athletes who used performance-enhancing drugs, LeMond told reporters, "I would have all the praise in the world for Lance if I thought he was clean, but until Dr. Ferrari's trial, we can't know for sure." He later apologized, but the damage was done.
Is Forgiveness an Option? Not with (naturally occurring) testosterone levels this high. In June 2006, LeMond told the French newspaper L'Equipe that he'd recently testified in a legal dispute involving Armstrong and that Armstrong had "threatened my wife, my business, my life." Armstrong, meanwhile, is playing the nut card. "Greg is just not in check with reality," he responded. "He's obsessed with foiling my career."

Pipín Ferreras and Umberto Pelizzari
Freedivers
Friends Forever! In 1988‚ when they met at a photo shoot, Italy's Pelizzari owned the record for static apnea (he'd held his breath underwater for five minutes and 33 seconds). Cuba's Ferreras had the "constant ballast" record (with fins, he'd plunged to 226 feet). As the pals began battling good-naturedly for the "no limits" record (they traded it back and forth four times between 1990 and 1993, reaching depths from 377 to 410 feet with the aid of a weighted sled), they let reporters think they were bitter enemies. "We wanted to milk it," Ferreras wrote in his 2004 book The Dive. "After all, without the media, we were nothing."
Oops: Chalk it up to oxygen deprivation—or the clashing of two giant egos—but by the mid-nineties, the faux feud had become reality. Ferreras once refused to even stay in the same hotel as Pelizzari. Neither will pinpoint what happened. "It's normal in any sport," says Pelizzari. "When you compete, the challenge gets bigger and bigger, then it creates a separation."
Is Forgiveness an Option? If whales and barnacles can have a symbiotic relationship in the deep blue, maybe these guys can, too. "I don't see why not," says Ferreras. "All he needs to do is say hello." "I'm not angry at him," offers Pelizzari, "but you have to tango together; you can't tango alone."