"Can you do a reading to see if my ex-boyfriend is still with that skank?"
"I want to do "this terrible thing" to this girl. Will I get busted?"
"I think that "Guy at work" is stealing. Can you see that? No, he doesn't work for me, I just want to know"
First of all, ew, no.
Secondly, I get these requests on occasion. I call them venom readings. The client isn't looking for their future, they're looking for someone else's. They're also looking for revenge.
Tarot readings are proprietary. I don't read for other people in your reading. If you want to know what influence Mr. X will have on your life, we can do that. If you want to know if Mr. X is still happily married to Mr. Y and if they'll ever divorce? That's none of your damned business. It's none of mine, either, unless Mr. X or Mr. Y come to me for a reading.
Tarot is not an excuse to spy or snoop on people, regardless of how badly they've hurt you. It's a way to seek your own healing and healthy choices, not a way for you to feel superior to others.
There is a saying that I use a lot. Too often, honestly, more people should know this. I'm going to teach it to you now. Ready?
"This is not my story to tell"
If you're looking for permission to snoop in someone's life, you're not going to get it from an ethical tarot reader. If you have nothing better to do with your time, you might want to reassess your priorities.
Poison poisons the poisoner. It might be slow acting, but that venom is going to get you in the end.