I am personally responsible for ruining the career of one of my former coworkers who was a nice guy and did absolutely nothing wrong to me.

I was a contract-to-hire employee with my job and it was in my early 20s. For the first 3 months of my job, I was put in charge of training me. The guy in charge of training me was a very nice and extremely intelligent guy, and a very good teacher. I was actually kind of startled by just how smart he was, because he taught me the job we do in a single day, and he could answer every single question I had, and then on day 2, he started showing me how to do the job with extreme precision and speed. Now, I was not stupid, but it was clear to me that he had a way higher intelligence than I did.<br><br>The issue with him was he had very little social skills. He would always be very blunt and to the point, and he could not read body language or facial expression that well. He sometimes would take a little too long to understand the joke that was being said. <br><br>I was delighted to have such a great trainer, but I was furious that he was so much smarter than me, and I was jealous. I also did not like how he sometimes had a hard time picking up on what I was thinking in terms of my body language and tone.<br><br>I started to make mistakes intentionally, and then I would have him retrain me on the subject I messed up on, which he would happily do without complaint. Then, I would say to the manager that my trainer was teaching me incorrectly, and since I was the one training for the job, the manager would trust my word, as opposed to his. I started to immediately gain a bad reputation to everyone else except my trainer. <br><br>Everyone in the department, including the higher ups were starting to not like me. They would let me hear it, but I did not care because I felt I had a personal vendetta against my trainer.<br><br>The problem was that my trainer and I were the only two on our team, and my trainer did not make any mistakes. His mistake rate was close to zero percent, and he was the most efficient person in the department. So when I would mess up, and it was his fault, it would throw the entire department off.<br><br>His boss would come up to him and scold him for it, and he would be very surprised that he messed up. He would go into every detail of what he taught me, and he would show that there is no way that I made the mistake that I did. He was right, and my boss knew that, but he did not care because he was trying to make sure that I had the right training. <br><br>I continued my tactics for another season, and then I finally got the job, and when I did, my trainer was let go. He had done absolutely nothing wrong, and he had been a stellar employee for years, but because of me, he was let go.<br><br>I had no reason to do what I did to him, and he could have had an extremely successful career in my company. I ruined his career and his reputation and I am not proud of what I did to him. I still think about what I did to him every single day.<br><br>Edit: Wow, this blew up without me even realizing. I am not in touch with him and I doubt that he remembers me. <br><br>Edit 2: I was not fake making mistakes to get him fired. I was actually making mistakes because I was a genuinely bad employee. I then used those mistakes to get him in trouble.