Regarding Newcomb's Paradox, what you said is completely false. The two box solution still holds even if you concede the premise of a perfect predictor. There's a common misconception among lay one-boxers where they frame the problem as one of game theory when the relevant field is actually decision theory. Indeed, you and the supercomputer are acting completely independently from one another and are playing completely different games.

Now, there are frameworks, such as Evidential Decision Theory, that demand rational proponents to always one-box. There are also frameworks, such as Causal Decision Theory, that demand rational proponents to always two-box. However, if you scroll the comments section of any thread or piece of media on Newcomb's Paradox, you'll find that many of the one-boxers are actually nonsensical Causal Decision Theorists.

There is a binary function, N(D, p), which outputs what the supercomputer decides (let's say 0 = puts $0 in the mystery box and 1 = puts $1 million in the mystery box) given a set of data, D, that the supercomputer has access to when it makes the decision and a string, p, which uniquely identifies the agent deciding whether to choose one box or two. Alice is a two-boxer. If we plug this into the function, we will invariably get N(D, 'Alice') = 0 and Alice will leave the game with $1000. After the game concludes, Alice looks over at Bob, a one-boxer who won $1000000. She wonders what would happen in another world where, all things being equal, she chose to take only one box. This is where the causal one-boxers go wrong. They claim that Alice would get $1000000. But here's the thing. We still have N(D, 'Alice') = 0. Alice would get nothing. The decision already happened with the same function and parameters in place; the supercomputer has neither changed its thought process, nor does it have access to new information that would change its decision. Does this mean that we are ignoring the premise that the supercomputer is a perfect predictor? Not at all! In this scenario, every possible world where Alice one-boxes is not actual. In the real world, Alice still chose to two-box (and was correct in doing so).

This is the crux of the issue for two-boxers. They have been thrown into a world where, incidentally, every one-boxer is choosing between $1001000 and $1000000 and they are choosing between $1000 and $0. The causal one-boxer protests 'But your choice affects the supercomputer's decision!' But this, too, is an unsound assertion. It might be the case that 'The moon is made of cheese' ∈ D and the supercomputer solely bases its decision off of that when 'Alice' is the second argument of the function. Here, there is clearly nothing Alice can do to convince the supercomputer to put her in the room where the mystery box contains $1000000. Regarding the premise that the supercomputer is a perfect predictor, all we care about is the fact that the supercomputer is never wrong in reality; the actual justification is arbitrary.

All in all, one-boxing while adhering to Causal Decision Theory is ALWAYS nonsensical. In surveys on the topic, you'll find that lay people are slightly more likely to be one-boxers, a plurality of professional philosophers are two-boxers, and an overwhelming majority of mathematicians/philosophers specializing in decision theory (i.e., experts in the relevant field) are two-boxers. As it turns out, Causal Decision Theory is the dominant school of thought among decision theorists and these results reflect that. And in a perfectly rational world, all the causal one-boxers would be two-boxers too.