Warnings: if you haven’t read chapter 357 of Hunter x Hunter, then it’s gonna be spoiler so don’t go any further if that's the case; bad grammar; unedited; typos.
「甘えてんの?」 - what does this mean?
In the JP-EN dictionaries, you'll probably mostly see the following definitions for 甘える:
To be someone spoiled or to act like one (e.g. demanding attention, asking for things, seeking affection)
To take advantage of or depend on (an emotion, goodwill, feelings, etc.)
Others also shared the other meanings in the following: Link 1, Link 2, Link 3 (you can google '甘える' and read HiNative forums too or other forums as well; you might need a google translator if you’re gonna go to a Japanese forum or read something in Japanese)
Here's what the dictionary I tend to use for Japanese classes say: Link 4
(Also, it may also have to do with this concept of 甘え, which exists in the Japanese culture to understand: Link 1, Link 2)
When I first read the official raws, I assumed Hisoka was saying something along the lines of "Whining like a little spoiled brat, are you?", "Demanding my attention, are you?" or "Being a spoiled brat, are you?". Because I wouldn't be surprised if Hisoka sees Machi's anger as an act of a spoiled person or some sort.
So I went to check if that's also what the translations would say. When I read the unofficial and official English versions, I was kinda surprised at their translations. Well, more like shocked for the unofficial one actually.
The unofficial English translation goes like this:
On the other hand, the official one goes like this:
I get that the official English translation went for the second definition of the verb 甘える, assuming that Hisoka was talking about his love for her or whatever that love is. The only problem is that we don't really know if he was really referring to love, goodwill, or whatnot. So it may makes sense, but not perfectly capture the whole thing.
But on the unofficial translation? I don't know what the translator(s) of the scans were on when doing this page or chapter. I guess they derived the meaning the word, 甘い. It can mean two things: 'Sweet' & 'Naive.' It uses the same kanji as 甘える, and probably assumed the verb itself meant 'being naive' or something like that. So, the translation ended up being like 'Being naive, are you?' and then the proofreader and the QC person probably were like 'uhh.... let's make it more natural in terms of the situation'. As a result, we have that line of 'Excuse me? Who do you think I am?' line.
I also searched for the Korean translation of this page to see how they translated it, and I'm lucky I found it on Twitter.
They translated it as 'Making a fuss, are you?', 'Being whiny, are you?' somewhere along those lines. Basically close to what I assumed when I read the original Japanese line. But obvs, it may not be exact.
So to answer the question, 「甘えてんの?」 does directly mean 'Acting like a spoiled brat, are you?', 'Whining like a brat, are you?', 'Seeking my attention?' or somewhere along those lines according to the first definition or others in those links. It makes a lot more sense in the context, considering Hisoka's vocabulary and personality.
But then again, Hisoka is into those double entendres sh*t a lot, so while he may be saying those lines, he might also be referring to some sort of feeling like he might be saying 'depending on my good will or favour or love for you?'. Or he could also have a third meaning on it. Who knows wtf this clown was on or was thinking about at the moment.
Anyways, this was a hard one because there's many ways to translate this, and since there's limited space on the speech bubble, translators have to pick the one that suits the most. Honestly, even I had to think about what Hisoka might be or what else he might expressing in that question whenever I had to re-read it.
Please share what you think is the meaning of that phrase now that you know what the verb means. This is probably the only time I want other people's insight so much on this.
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PS: @wurud, I tried my best to answer as you requested. I hope it helps you understand what Hisoka means in this panel.