1、you'd better not do something
You'd better not ask for trouble.
（ask for trouble自找麻烦；自讨苦吃：persist with actions or an attitude despite the probability that it will cause trouble）
2、It's better not to do something
It's better not to ask him why.
3、You don't wanna do this.
You don't wanna mess with me, trust me.
mess with 招惹，打扰：PHRASAL VERB If you tell someone not to mess with a person or thing, you are warning them not to get involved with that person or thing.
You are messing with people's religion and they don't like that.
The trees interfere with the view.
Smoking often interferes with health.
The doctor said that the girl had been interfered with before her death.
Who interfered with my papers?
You have no right to tamper with others' affairs.
He tried to tamper with the witness.
to tamper with a jury
to tamper with the text
Someone has been tampering with the machine.
He has been tampering with her feelings.