WARNING: The following contains spoilers for X-Force #14 by Benjamin Percy, Gerry Duggan, Joshua Cassara, Guru-eFX, Tom Muller, VC's Joe Caramagna, and, Tom Muller on sale now.
Although the X-Men ultimately walked away with a victory, the mutants' backs were up against the wall in "X of Swords." They lost one of their closest teammates warriors in a duel to the death, and the situation only got worse as the non-lethal contests against the warriors of Arakko aren't going the X-Men's way.
While Krakoa's champions have lost a variety of contests in the tournament. X-Force #14 gave Storm a chance to prove how deadly she really is in a one-on-one duel with Death.
Storm and Wolverine won a drinking contest for Krakoa by default in the previous round. At the time, the biggest side effect of the liquor was the renewal of their romantic chemistry. Unfortunately for Storm, the liquor came from the poison realm Blightspoke. It may taste sweet, but it has a serious effect on mutants, draining them of their powers. While Wolverine's healing factor means it will filter out of his system before his next battle, Storm wasn't as lucky. Storm awakened for her battle with Death hungover and powerless. It looked like she might be poised to join Captain Britain among the fallen X-Men. Death even offered her a chance to forfeit, which only fired Storm up, causing the usually composed X-Man to utter a rare curse. Storm proved to Death that it's not her powers that make her one of the strongest X-Men, but her will. She took the fight to him, destroying his blade with her knife.
With Death vulnerable, Storm hit the finishing blow, stabbing him in the chest. Her parting line, "Well... he's bleeding, isn't he?" is more than trash talk. It's a cue for a swarm of undead spectators to run in and devour Death, taking him off the board for Arakko.
If Death had done his homework, he might have known how deadly Storm can be with a knife in her hands. In Uncanny X-Men #170 by Chris Claremont and Paul Smith, Storm challenged the leader Morlock Callisto to a knife fight for the leadership of her tribe. Callisto took Storm lightly and, physically, she was weak due to the Morlock plague. Beyond that, Callisto didn't believe Storm had it in her to win a fight to the death and she paid for it.
Storm won the duel but showed Callisto no mercy, seriously wounding her to achieve victory. Callisto only survived because of a Morlock healer. Years later, Storm fought another Morlock, Marrow, in another duel but this time, she was fighting for the lives of hostages as Marrow was threatening to kill by detonating a bomb in her heart. Storm won this duel too, tearing Marrow's heart out to neutralize the threat of the bomb. Like Callisto, Marrow survived, thanks to her healing factor.
Storm didn't learn her knife skills in the Danger Room, but she picked them up growing up on the mean streets of Cairo, Egypt. After being orphaned she worked as a pickpocket. Until her mutant powers developed, a blade was her only protection. She had to use it once as a child to fend off a predator, killing him, which led to her vow against killing. She's had to set this vow aside entirely during the Otherworld tournament, where everyone's playing for keeps. As Death learned, it's not wise to underestimate her in a deathmatch, especially when the knives come out.