Any gift that suggests they need to improve something about themselves, especially if they’ve never shown any interest in that. Like a gift card for skincare treatments, or teeth whitening. Maybe a self-help book, or some exercise equipment. Cologne/perfume is good for deniability, but it might come off as more romantic than intended.

Also, giving any of these gifts to make someone feel bad about themselves makes you an enormous asshole. Use your words, be honest with people, and don’t go out of your way to humiliate or irritate people you don’t like. Life’s too short to spend it scheming.

Most folks have at least 1 commonplace food item that they can’t stand. This time of year food gift baskets are everywhere and often specialized to certain tastes. So you get them something that looks like a nice goodie basket but then most things in it are tainted by a thing they don’t like.

For me it would be licorice / anise.

My personality disordered MIL is an artist at giving insulting gifts. An absolute master. She likes to pretend she is very poor, although isn’t, and she volunteered at a Catholic charity shop for used goods, so she would take home armloads of used crap donated from the homes of deceased elderly people and would give them as gifts, none of which was any use to anyone and was quietly donated elsewhere afterwards. But she also likes to give you weird things that are basically trash, not because she can’t afford gifts, but just to get negative attention and make people upset.

1. She gave me her old used bathrobe as a Christmas gift, which was pretty threadbare, and made sure to call me the next day to tell me it had been hers, which I had consigned to the garbage because it wasn’t even really fit for donation.
2. She gave her only granddaughter an old vitamin bottle filled with dish soap and a discarded bubble wand she had found in the park. Not even one dollar for her grandchild would be spent, hell the dish soap probably cost more than buying a bubble blowing kit from the dollar store would.
3. She gave my BIL a sandwich baggie filled with used discarded golf tees that she had picked up walking the public course, all chipped and full of dirt. Another item easily found at the dollar store.
4. Years later her only grandchild had developed an eating disorder after being bitten on the face by a pit bull and needing several surgeries to repair as she was depressed about her appearance, poor kid. My MIL immediately went out and bought herself some size XXXXL pyjamas, and then dramatically announced to her grandchild’s mother/her daughter that they were too big and she was going to give them to her grandchild, who is way thinner than her and would never fit them. We intervened and told her she was not to do that, and she immediately began squawking about what she could possibly do with them now. The whole point, if you don’t speak personality disorder, was that she bought them simply to give them to her to send her a message that she was fat, even though she was absolutely not, and to also upset her daughter.

Top tier personality disorder behaviour really.