Getting even with someone requires two things: a reason and a method. As this OP writes, they have a reason, and they have the method, for revenge.
The Lazy Husband Gets His Due
Not me, but a married couple my family was friends with long ago.
The husband was lazing about playing video games all Saturday morning while his wife kept nagging him to help with chores around the house. Eventually, he decides to go take a shower. On his way, he notices wife is doing laundry. He jokes that fresh boxers from the dryer would be a real treat & she waves him on.
But incidentally, she did happen to have boxers in the washer at that time. She goes to switch loads & reaches for dryer sheets. While doing so, she notices a bottle of spray cat nip. She sprayed cat nip all over that pair of boxers & dutifully handed them to him when he got out of the shower.
He goes back to his chair & plays his video game. She just so happened to let the cat in. The cat proceeded to attack his crotch. She let this play out for a while before she let him in on what she did. At the end of the explanation she added “& you don’t know that I only did it to one pair”
She caught him in the act of sniffing the crotch of his boxers for days. Then changed fabric softener & laundry detergent. He noticed the change in smell & was very suspicious.
Completely unrelated, but they happen to be divorced now.
The Final Word
Catnip is a great way to get someone noticed by cats, inside and outside. Use the catnip wisely and ensure the person isn’t allergic to cats before spraying their clothes. Of course, there are other things you can do to the clothes of someone to get even with them. Personally, I like adding a couple of threads to their socks, a single stitch or two in the toe area will keep the toes from going in and cause them a lot of grief with just a little effort. And removing the head of the zipper to the zip-up fly is good too.