1. I was late and he was furious at me. [Correct]
2. He's furious with the way he's been treated. [Wrong]
furious with someone [Correct]
furious at someone [Correct]
furious with something [Wrong]
furious at something [Correct]
Cambridge Dictionaries Online - Cambridge University Press
- I was late and he was furious with me.
- He's furious about/at the way he's been treated.
- We had a furious row last night.
Merriam-Webster's Learner's Dictionary
- She's furious at/over how slowly the investigation is proceeding.
- I was furious with/at them for printing the story.
- a furious argument