well first off she pretty much instantly beats any technology based hero/villain or any one with cybernetics (i.e. iron man, iron patriot, cable, bushwacker, deathlok)
and beyond that she can kill pretty much anyone she wants in the MCU in a couple different ways
first she could just straight up ghost your heart (or brain or any other vital organs) out of your body like she did to Emma Frost (notice how her diamond skin did squat to stop her)
or she could scramble your brains (and I’m pretty sure even people like thanos and apocalypse have some kind of squishy meat brain)
also, while she’s never done it, she could just phase you a mile below the surface of the earth (or even just a wall) and leave you there or easily leave something like a peddle in your brain or heart and there isn’t really anything you can do about it because even if you see her coming from a mile away as long as she’s intangible their’s nothing you can do to stop her, not even psychics can effect her while she’s phasing. seriously kitty pryde’s powers are one of the most under utilizized (and feared) things in the marvel universe
I remember when she joined the X-Men. Prof. X devised this whole elaborate sequence in the Danger Room to test her powers, and she just walked straight across the room with her eyes closed.