きたんだろう at the end


I am bit lost by the きたんだろう in this sentence.

あれはお前が勝手にしてきたんだろう

something like you do what you want with me? I read somewhere that this きたんだろう
means something like the speaker "knows" what to do. but i am totally
confused.




Context is king! I'll try to answer your question, but trying to do it without
any context is a pain in the neck.

  1. だろう is the form of でしょう, which you use when speaking with a person you're familiar with and you can afford to use it.

  2. ん is a contraction of の.

These two forms original, dictionary form would be んだ, alternatively のだ or
のです. でしょう (or だろう) when linked with の/ん forms sort of rhetorical question. The
speaker seeks agreement, he's not really asking the question.

  3. te-form + きた indicates that an action has been taking place over some period of time.

  4. 勝手にする means "to do something selfishly".

With these 4 points in mind, I believe the right answer to your question would
be something along the lines of "I guess, you've been doing that without any
regard to anyone or anything, haven't you?!"

