This is entirely my own opinion. Yours may be different, and that is okay.
Working "negative" magick to try and hurt someone for petty reasons, to me, is incredibly childish. Is is acceptable to punch someone in the face because they annoy you? Or because they have something you don't? No, of course it isn't. If it isn't appropriate to hurt someone physically, why on earth should it be appropriate to do so magickally?
"But if someone throws negative magick at you, you should retaliate!" I reject that notion. I think you should learn to protect yourself magickally instead. That works physically, too -- it is always better to be able to deflect a punch and subdue an attack than to swing wildly back, risking further injury. With hexes or curses, the simple fact is that you don't need to retaliate, because the universe will do that for you, and you can help it along. Learning to reflect bad magick or let it pass through you is far more useful than learning how to hex, less risky, and overall better for you.
Look, let's use a fairly childish and base metaphor. Someone using negative magick against you is like someone walking into the room you're in and throwing a stink bomb at you. Gross, right? Of course. So what's the best thing to do?
1) ignore this childish person, turn on the fans and open the window, allowing fresh air to come in, and afterwards close the door so they can't come back in,
2) throw a stink bomb back at them immediately, adding to the stench in your room. Eventually they'll walk out, but your room will still smell foul, and it will be partially your fault, now, too?
Cursing and hexing is like that -- it just stinks up your stuff! It's better to protect yourself and learn to bounce it back at the hexer. Turn your fans on and open your windows; or even better, maker sure the door is closed so the dreadful person can't come into your room in the first place!
I do understand that feeling a 'need' for vengeance is a very human desire, and it is powerful. Sometimes trying to live with that desire is painful. I have always found that invoking someone's "karma" (I know that's not the precise term for how it works, and fairly culturally appropriative to boot, but until I can think of a non-clunky term, I'm afraid it will have to do....just be aware I'm not speaking of karma in its proper Hindu sense) is of far more use than cursing or hexing. It can relieve that pressure that a need for vengeance calls for, and it's working with the natural forces of the universe. It can be so, so cleansing for you.
This sort of invocation can become a beautiful symbol of your trust and love for the Goddess -- leave this complex, painful desire (note that I didn't say immoral!) in the hands of the Goddess, and She will turn that energy into something better for you, she will clear it from you if you ask Her to. Trust Her!
A lot of people would sneer at that and say that this is a passive move. I disagree. This is "do no harm, but take no shit" in action. I am not bringing myself down to someone vile's level and harming them, but I am certainly not taking their shit -- I will protect myself magickally, and I certainly wouldn't happily let someone who curses or hexes me or anyone I love stay in my life. One can absolutely take no shit without harming anyone.