maneiras de dizer "falar mal de alguém" em Inglês

I remember the first time I was talking to a guy from the USA and I was telling him that there was someone saying bad things about me at school. The problem was that I didn't know exactly how to say that. As simple as it might sound to you depending on your level of proficiency in English, when you're first confronted by something more idiomatic in English you tend to be shocked and your mind goes totally blank.

But let's try to stay focused here: what are the possible ways to say someone is saying bad things about you? Notice I've already mentioned twice the first way to express that idea in English: to say bad things about someone. If you happen to be just beginning your studies in English, that might be the first option that crosses your mind. That's the simplest and most obvious option after all. But the reason why I'm creating this post is that I've found many other ways to say the same thing. Those other less known expressions sound more natural to a native English speaker and can take your English to the next step and a higher level. Here are the expressions:

To speak ill of someone: I refuse to speak ill of any of my friends. Max speaks ill of no one and refuses to repeat gossip.

To bad-mouth someone or something: Mr. Smith was always bad-mouthing Mrs. Smith. They just didn't get along. John bad-mouths his car constantly because it is too small for him.

Run someone or something down: Please stop running me down all the time. I can't be that bad! You run down everybody who takes your old job!