Interested in Language
Hello, I'm not sure how to answer this. I don't know which grammatical rule to apply.
His anger______me had little justification.
It's not a matter of a grammar rule as such - it's a matter of what people say. 'At' and 'against' are used, but 'with' is far more common.
Once your homework has been corrected/marked, we can then help with anything you don't understand.