Who can explain the pun/wordplay on “onitada” in the story “Jaku-Chara Tomozaki-kun”


In the Light novel / Manga / anime : 弱キャラ友崎くん (Jaku-Chara Tomozaki-kun), the
main heroine regularly says “ONItada !” (translated by “HEXactly !”).

What would be the “de-pun-ed” word or how (from what words) is that word built
?

EDIT : to make myself clear, I'm mainly interested in a lexical answer (even
if the syntactic and contextual aspects are also interesting)




Since the question was explicitly asked to be more about the lexical
construction than about other considerations, and that the other answer eludes
that point. Here what I wanted to accept :

It is built as the abbreviated composition from 鬼(oni)+正しい(tadashii) ⇒ 鬼正
(onitada). for more considerations about the meaning and using context, see
[Naruto's answer](https://japanese.stackexchange.com/a/86850/27954).




It's not a pun. According to sources, it's abbreviated 鬼のごとく正しい ("correct like
an _oni_ ", "demonically correct"). It's not a set phrase ordinary people
recognize. The heroine somehow liked this funny phrase after seeing it
somewhere, and started using it as a pet phrase.

I have no idea where that HEX in the English translation came from.

See: <https://rightnonel.com/archives/760>

鬼 can be used as a prefix meaning "super-" (e.g. 鬼かわいい, 鬼やばい). Although it's
uncommon and slangy, young native speakers who are good at slang should be
able to intuit the meaning of おにただ without explanation. See:
<https://gamp.ameblo.jp/wasansensei/entry-12592348963.html>

