The following article contains spoilers from Mary Jane and Black Cat #3, on sale now from Marvel Comics.
When people think of the Black Cat, they imagine one of the greatest thieves in the Marvel Universe, but the fact that she does have powers isn't common knowledge. Specifically, she has the power to subconsciously afflict those she perceives as enemies with bad luck. This power has come in handy more than once, but in Mary Jane and Black Cat #3 (by Jed McKay, Vincenzo Carratu, Brian Reber, and VC's Ariana Maher) it has become a problem for Mary Jane Watson.
When confronted by a monster, Mary Jane's questionable "luck" regarding her new powers made her realize that it was Black Cat's fault. This forced her to realize that her subconscious mind registered Mary Jane as a threat due to her anxiety over her new relationship with Peter Parker. In admitting this, it reveals that Black Cat's power has room for error if her own insecurities get the best of her.
Black Cat is Bad News for Mary Jane
The duo had been recruited to steal back the demon Belasco's soulsword from the Screaming Tower, a massive fortress that kept the sword safe from the denizens of Limbo. In the process of navigating their way through the structure, they came across the sword's protector, known only as the Guardian. Apparently, the tower was built not to contain the sword, but the creature itself, and when provoked was ferocious. Faced with the enormous monster, Mary Jane was left with no choice but to once again gamble her life.
Unfortunately, she ended up getting a useless power among a series of them since the adventure began. This confounded her, as she could not understand how her luck could be so consistently bad. Then she remembered Black Cat had the ability to bestow bad luck on people. When she told Black Cat this, it didn't make sense to her. Even though the power is used passively, it still requires her mind to perceive someone as a threat to give them bad luck. This forced Black Cat to realize that her stress over telling Mary Jane that she was dating Peter again was causing her mind to view her as a threat because she didn't want her partner to be angry with her.
Black Cat Has Marvel's Most Unreliable Power
This is a surprising revelation about a power that has otherwise been under her control. She first acquired these powers as part of a deal with the Kingpin, which granted her the ability to cause freak accidents to occur to those in her immediate vicinity. The caveat was that her mind must perceive someone as a threat to be affected by her power. For a time, she lost this ability after Doctor Strange tampered with her powers, but later regained them thanks to the intervention of Doctor Tramma, who gave her cybernetics to simulate the same effect.
However, she has never lost control of who it targeted before, especially when she needs all the help she can get to stay alive while fighting the Guardian. It demonstrates how her subconscious mind can override what she knows to be true. Her fear over how her new partner will react is so great that she unintentionally perceives her as a threat alongside the giant monster trying to kill them. In truth, she is letting her insecurities take control of the situation. Had she told Mary Jane the truth sooner, they wouldn't be in danger right now, and from here on out Black Cat will need to be mindful of how she perceives any future partners.