1. キモい / Kimoi
It’s totally fine to use it when you see something literally gross. You can use it to describe something that annoys you- anything but people.
But again, it sounds very offensive if you say it to someone. Even if you hear people using this phrase, you probably should just avoid using it altogether.
2. ウザい / Uzai
Uzai is also used for anything annoys you. It sounds softer than kimoi, but still not good.
3. 死ね / Shine
You hear it often when you watch anime in Japanese, but it’s used when killing actually happens in anime, so it’s fine there.
However, some people use this word lightly, and it can really bother people. I hate it!
4. くそ / Kuso
You can just say “Kuso!” like “F**k!” when shit happens.
Kuso-yarou means “bitch”, “sucker”, or something like that.
You can also use it to emphasize what you want to say. For example, “atsui” means hot in Japanese, and “Kuso atsui” means “f**king hot”.
Not appropriate at all, anyway.
5. キチガイ / Kichigai
It used to be used during World War for people who had actual mental problems because of the war. This word became common again these days, because people started using on the internet.
Anyway, don’t use this word either.