Fans know Wonder Woman as an expert fighter, trained from an early age to triumph in battle - but when she fought Storm of the X-Men, the Amazon made a dreadful and embarrassing mistake. Marvel and DC Comics have crossed over before, but in 1996, the two companies worked together to create the ultimate crossover event: Marvel vs. DC (also printed as DC vs. Marvel). In Marvel vs. DC #3, written by Ron Marz with art by Dan Jurgens and Claudio Castellini, the two superheroes finally meet in single combat.
Marvel vs. DC tells the story of two ancient cosmic entities known only as the "Brothers", each representing an entire universe. The Brothers have noticed one another and wish to fight - but should they even come to blows, both universes would be destroyed by the sheer power on display (an earlier clash resulted in the Big Bang). Thus, each Brother chooses champions to fight in their stead: heroes and villains from the Marvel and DC universes. Superman fights the Hulk, Batman fights Captain America, and Wonder Woman is set to battle Storm (and the universe that loses the most fights will be destroyed). To complicate matters, a small but important weapon finds its way into Wonder Woman's hands: Thor's hammer Mjolnir.
Wonder Woman manages to lift the hammer (both she and Superman are canonically capable of holding Mjolnir), granting her all the powers of Thor...a God of Thunder. It's here where she encounters Storm; she's quite familiar with the weapon and knows she's at a severe disadvantage. Still, she intends to fight on. "I, too, have been called a Goddess, and the lightning is at my command as well." It's here that Wonder Woman makes a critical mistake: she drops the hammer, relinquishing the powers of Thor. According to her, the battle "...would not be fair" if she held Mjolnir while fighting Storm.
"We face each other as was intended!" Wonder Woman shouts - and while her actions are noble and admirable, they're far from wise. Storm utterly dominates Wonder Woman during the fight, summoning powerful winds, pouring rain, and finally a powerful bolt of lightning that finally brings the Amazon down for the count. Honor in battle is usually Wonder Woman's way, but billions of lives are at stake, not just her own. As an Amazon warrior, Diana was foolish to throw away a powerful advantage that could have easily helped her win the fight.
The ending of Marvel vs. DC is ultimately a happy one - the Brothers stand down from their fight, both universes continue to exist, and only the heroes remember shades of the crossover. But fans remember everything - including the time when a warrior lost a fight to save a universe for the sake of being fair. Wonder Woman lost because she was too heroic - and against a powerful opponent like Storm, chivalry is not a winning strategy.