You better be right! の意味は？

You better be right!
I'm sorry to say despite not knowing this phrase.
I suppose this phrase might be a title of movie/lyrics/novel/etc. I suppose the translation sentences might be translated by the writer/musician/author actually.
I suppose it might had been translated amid the scenario/mood/story. you had known the content and context already, you could have felt some complex feeling.
the only thing I can do is to search the relevant reference.
the answer I can do to your question is this extent.
I would like to be some help for you.

:You better be right!
https://ejje.weblio.jp/content/You+better+be+right%21+
:Using 'Had better' - English Grammar - Gymglish.
https://www.gymglish.com/en/gymglish/english-grammar/using-had-better

You had[should] better be right.のhad[should]が略された英文　　だろうと思います。

had better は　そうしないと　困ったことになるよ　という警告・忠告　
状況によっては喧嘩腰なので

正しいことをしないと（〜正しいことを言わないと）　困ったことになるよ　　　を

言ったわね　　と訳するのも　良いように思います。