Working is a thing we do to make money, to spend on things, then we work more to get more money. Working should be enjoyable and trouble-free, so I have no issues with this OP’s story about getting an asshole coworker fired.
Getting the Jerk Coworker Fired
Back when I worked at a grocery store, the rule was that the guy in the dairy cooler would cover the cashiers’ breaks in the evening. Another rule was that the tills could only be $5 above or below the expected amount at the end of the night.
So when some hipster dickhead started making crappy comments about every little thing I did, I got sick of it pretty quickly. He once sincerely ridiculed the way I chewed two pieces of gum at once, saying “OOOOOOOH YOURE SO MANLY DUDE, THATS SUPER MANLY MAN DAMN YOU MUST BE TOUGH.” He would make comments like that basically every day, so I started throwing his till off on purpose during his break. I would “accidentally” give out more change than I was supposed to, and he would often be more than $20 off at the end of the night.
One time I was talking to my work friend about how I was replaying Pokemon Blue Version, and dickhead jumped in with a “WOW, I DIDN’T KNOW THEY HIRED CHILDREN HERE, HAVE YOU TRIED GETTING AN ADULT HOBBY?” So that night, he mysteriously wound up ~$50 off on his till and got fired on the spot.
He was still an asshole every time he came into the store, but it still felt great.
The Final Word
Your job doesn’t define you and your coworkers need to respect you. When this doesn’t happen, you’re free to use what is at hand to get petty revenge.