The question is quite straightforward - I did not include my research as it only resulted in synonyms for the word "opposite".
The context is that something is completely different to what you expected it to be and suddenly you feel the urge to exclaim: "Oh, that's exactly the opposite".
Or even if you are arguing with someone and they have a completely different idea of what the situation is, so you want to tell them that everything is... well, exactly the opposite, ha-ha!
Thank you for helping me in advance! #NonNative