I've only had one terrible interview as the candidate, but there's one I conducted myself that weighs on my conscience. It was my first job in IT, and I was still a student back then with no real experience to speak of. A young guy came in to our company who was clearly very stressed, and I kept asking him hard questions - probably not to actually assess his competence, but to prove that I was the one who knew my stuff. That was 20 years ago and I don't remember the details anymore, I only remember that he was stressed and I just treated him cruelly with those questions. It wasn't anything offensive, I just keep recalling that moment and I regret it. Today, if I were conducting any interviews, I would make a real effort to make the person feel comfortable, even if they don't know everything or are a weak candidate.