Expressions used in Everyday Spoken English in Social and Professional contexts
(get/be) on somebody's bad side
on somebody's bad sideget on somebody's bad sidebe on somebody's bad side
Meaning(s)
1) do something or behave in a way that angers somebody or causes them to dislike you
How to MemorizePopularity HighProfessional HighSocial
you don't want to be on his/her bad side
Analysis
This idiom is usually said in relation to somebody in a position of power or authority, or who is considered dangerous in some way. When preceded with the word 'don't', as it often is, it becomes a warning. Often, you can 'get on somebody's bad side' accidentally through something you said or did, without realizing it would cause offence or be received in a negative light. It is common in both a social and professional context in an informal way.
Social Examples (Basic)
I think I got on Sarah's bad side at the party because of my boorish behaviour. Hopefully she will accept my apology and not hold it against me.
Professional Examples (Basic)
Mike is someone with a lot of power and influence in the industry. You really don't want to get on his bad side.
I don't want to be on my manager's bad side, but at the same time I can't just let her walk all over me.