How to say 'Don't do that' in Korean

1. 하지마

• 하다 = to do
• 말다 = to not do
• 하지 + 마 = don't do that

To tell your friends to stop doing something, say: 하지마.

2. 하지 말라고 했다

• 하지 말라고 = Don't do that (when telling someone a second time)
• 했다 = did (past tense of 하다)
• 하지 말라고 했다 = I told you, don't do that

In those situations when they just won't stop, and you have to tell them a second time, say: 하지 말라고 했다.

3. 아 쫌!

• 아 = Ah (exclamation)
• 쫌 = abbreviation of 조금

When they still don't listen, exclaim this as if to say 'Come on! (Listen to me)': 아 쫌 (하지 말라고)!

4. 적당히 해

• 적당히 = moderately, enough, just right
• 하다 = to do
• 적당히 해 = hey, watch it.

This is more of a warning to let them know not to cross a line: 적당히 해라.