Some questions about だけ and clarifications about its nuances

Question

The girl who just spoke is clearly being a pain in the ass, and after she leaves, one of the boys says this :

1 - オレ憎たらしさには　自信があったが　あいつだけはぜったい勝てん。

I was sure I was unpleasant, but it's nothing compared to her.

I'm used to see 勝てる　used with に, which here is replaced by だけ which confuses me a bit.

It doesn't seem to mean "only her", or maybe in the sense "I'm still more unpleasant than anyone, except her"?

The thing is the contrastive は combined with に seems to have this meaning already, "I can't win against him VS I can't win against him (though I would win against others)"

in this question : sometimes だけ gets mildly confusing.. someone suggests that in example 2, だけ is juste used to stress は.

2 - それだけは、食べないでください。 "Please don't eat that. (Eat anything else.)"

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Long story short, what would be the difference in example 1 if だけは was replaced by the following (my guesses on the right)

に - Just a simple relation : I'm nothing compared to her.

は - Same as には but with a casual drop of the に as in 僕（に）は自信がある

には - Contrast : I'm nothing compared to her (though compared to ohers...)

だけ - Stressed version of に with a casual drop of に : I'm nothing compared to her (and her only, don't know about the others)

だけは - Stressed version of には with a casual drop of に : I'm nothing compared to her (and her only, though compared to others...)

だけに - Plain version of だけ

だけには - Plain version of だけは

All the versions without は dont feel right to me in a negative sentence.

Answer 1

「オレ[憎]{にく}たらしさには　[自身]{じしん}があったが　あいつだけはぜったい[勝]{か}てん。」

First off, this sentence is highly colloquial and the speaker omits a couple of particles. That may be causing part of your confusion. The conjunction 「が」 in the middle is actually a key word here that would help one understand the last half of the sentence.

"I had confidence in my own 憎たらしさ, but ~~~~~~~~."

「あいつ」 must be worse than the speaker in the degree of 憎たらしさ, n'est-ce pas? Otherwise, 「が」 would not have been used.

In this context (and not elsewhere),

「あいつだけは」＝「あいつだけには」＝「あいつにだけは」

「に」 is clearly being omitted as we say 「～～に勝つ/勝たない/勝てない」

"I was confident in my own wickedness, but there is no way I could beat her in that department."

Finally, here is what I would think if you replaced 「だけは」 with the following words.

「に」: Not natural. Needs 「は」 or 「だけ」 as well.

「は」: Possible.

「には」: Very natural.

「だけ」: Possible if not very natural.

「だけは」: Pretty natural.

「だけに」：Possible and slightly more natural than 「だけ」.

「だけには」: Excellent choice.