This post has been sitting in my drafts folder for almost 3 years so I decided it’s high time to get it out the door finally.
「逆に」（ぎゃくに） is one of those expressions that is used all the time. Even if you decide to stop reading the rest of this post because you hate me for being so cool, you’re probably going to pick it up somewhere along your studies.
「逆」 by itself means, the “reverse” or “opposite”, and is a pretty useful word by itself as you can imagine. It is used as a noun as shown in the following (admittedly cheesy) dialogue.
Tanaka) Going to submit your report tomorrow, right?
Miki) Um, yes!
Tanaka) Don’t slack off too much.
Miki) Yes! Understood!
A-san) I wonder why Tanaka-san is always hard on Miki-chan? Maybe he doesn’t like her or something?
B-san) I think it’s that exact opposite.
It’s slang, it’s not supposed to make sense!
While that’s all fine and dandy, you wouldn’t think adding 「に」 and making it an adverb would be a very useful construction. I mean, how often do you say “oppositely” in English? But in Japanese slang, it doesn’t have to mean what it actually means!
Miki) Thanks to this report, my date tonight is ruined.
A-san) Isn’t it oppositely good? You were saying you wanted to break up with your boyfriend, right?
Miki) That is true but it’s better than doing overtime.
As you can see from my crappy translation, 「逆に」 doesn’t have to be the direct opposite of anything in particular, really. It can be used to describe a result that might run counter to what you would normally expect. It can also be used to turn the tables around on someone (much like the title of this post).
I heard he got dumped by his girlfriend and when I tried to cheer him up, he oppositely got mad at me.
In fact, one very popular slang is 逆ギレ, which is when someone who is in the wrong turns around and gets angry at the person who confronted him or her.