In fairness to black cats, it should be noted that they are just like any other cat: they want you around and available for when they need you.
Otherwise, they’d really prefer that you mind your own business and not touch them unless prompted to do so.
The universal “okay-you-can-touch-me-now” signs are, of course, them brushing against your leg repeatedly or taking a seat right on the book you happen to be reading. They are just cats.
However, if you would like to tap into this widely-held (if a bit misleading) perception of mystery, a black cat tattoo is the perfect way to go. Realism is probably the best style to use in this instance, with the eyes and posture being of particular importance where conveying impending disaster is concerned.
Ideally, the cat should be calmly damning the observer to hell.
If you’d prefer to mock the idea of “bad luck” and superstition, you might try a design with a black cat walking under a ladder with a broken mirror nearby. The cat could also be wearing a collar with the number “13” on it.
If you’re going to tempt fate, might as well really lean into it. Some will get the over the top symbolism and rampant satire, others may have it go right over their heads. However, given that your ink should always please you first and be exactly what you want it to be, either reaction works.
If you embrace the idea that luck is made and not determined by fate or black cats, a design such as this will make that point in a fun way.