I want to have my 12 year old cat put down for repeatedly pissing on my bed
Have you tried training the cat?
I can't be bothered to do that.
Don't do this. There are ways to correct a pet's behavior. Use those before deciding to put the cat down.
I want to show her that she made me upset.
If you can't train her to use the litterbox you can surrender her to a rescue. They can try to work with her or find her a better suited home.