A common horror story could be related to the work - life balance during the internship. Imagine an intern who has to stay late every night to finish tasks, missing out on social and personal life. There could also be situations where the internship doesn't turn out to be what was expected in terms of the work content. For example, an intern might think they'll be doing creative writing but end up doing mostly data entry. It's a big disappointment and can make the internship a horrible experience.
Well, one horror story could be about an intern being overworked. They might be given tasks way beyond what's reasonable for an intern, like having to produce a huge number of articles in a short time with little guidance. Another could be dealing with a really difficult boss who is constantly criticizing and not providing any positive feedback. And there might be stories of interns being excluded from important meetings or discussions, making them feel like they are on the outside of the real work environment.