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One of the main problems with a “negotiated peace” is that it sends the message that with sufficient firepower any country can take new land by force and the rest of the world will be okay with it. Russia may see this and begin to forcibly remake much of the world with countries around Russia forced to either submit to them or face invasion. Russia may not attack NATO but if they can get away with military force that opens the door to full invasions and annexations in places like Finland, Kazakhstan, Georgia, Moldova, Belarus, Azerbaijan, Armenia ect. 
This also goes beyond Russia and it China sees Russia get away with land grabs then it opens the door for them to invade a whole host of countries. If wars of conquest are legitimized again it could cause global trade to break down, the reintroducing of protectionism, massive increases in military spending around the world and a new reality that’s much more dangerous than what we see now. The consequences of a negotiated peace in Ukraine for the US is an exponentially more dangerous world than we have today. Even from a strictly amoral utilitarian US prospective legitimizing Russian conquests is incredibly dangerous.
The biggest issue to me is a negotiated peace where Russia doesn't lose significantly, is the massive risk for nuclear proliferation. If more powerful countries can once again just invade less powerful countries, many of these will start to see nuclear weapons as the sole means of protection. Taiwan, South Korea, Japan, Iran, Finland, etc. would all likely want to go nuclear. >


Japan... would likely want to go Nuclear

The other countries are debatable, but there's just no way the Japanese public would accept their leadership using any kind of nuclear attack or weaponry.  Only 14% of the Japanese public approves of the use of nuclear bombs during WWII.  Unless there's a radical opinion shift, the Japanese government may continue to rely on an alliance with the U.S as their preferred form of deterrence. >

I mean no one wants to get nuked, everyone would like to be the one nuking others though >

I don't want to nuke anyone. I am sure there are plenty of other people who feel the same way, especially in Japan of all places. >

So your average Japanese person would prefer to be under Chinese occupation than to have a nuclear stockpile? >

That is a strawman argument. There is no reason to expect Japan will fall under Chinese occupation just because the country chooses not to use nuclear bombs. They are still allies to the United States and we are an excellent deterrent to Chinese aggression. >

US can easily stop being a dependable ally if Americans elect someone like Trump as President again >

Ukraine points out that Russia just cannot be trusted in the negotiations as they have broken so many promises in the past. 
Russia will not back out easily from the taken territory and any negotiated peace time will be used by them to rebuild army strength to attack again in few years. >

I think it was Mark Milley that said that the only way Russia seriously comes to the negotiating table is if Ukraine can seriously threaten Crimea. Because at that point Ukraine would have real leverage because Russia is at risk of losing territory (in the pre-2022 sense), and it’s one thing to not have anything to show for this war, but it’s another to go backwards. >

How exactly would this work. If Ukraine gets the capabilities to kick the Russians out of Crimea, why would Ukraine want to negotiate unless its prepared to formally cede some territory for Russia? >

A good reason for this, and I say this with my own personal beliefs being that Crimea should be returned to Ukraine, is that Ukraine's Western allies are enabling the country to fight for it's territory. Threatening Crimea is likely a strong line for both Russia and those allies that neither may want crossed. 
Russia will likely be in a very bad spot at that point and willing to drag the fight out longer, because Crimea represents territory they had and were likely going to keep before they committed to taking the rest of Ukraine. Losing Crimea represents a point where even Russia's allies may back out. They'd do anything to avoid that. 
The West likely sees Ukraine's ultimate victory in keeping what it has before the 2022 invasion, not retaking Crimea. At that point they might feel that Russia is significantly deterred from future incursions because of it's losses that they demand Ukraine negotiate. Alternatively, the West might get Ukraine to agree to negotiate in exchange for increased military aid for a few years, as a deterrent to Russia, and some more favorable terms for Ukraine paying back the aid they received. 
Speculation, obviously. And I kind of hope they continue until Crimea is returned, but this may be why this ends before Crimea is retaken. >

Until Russia decides again to "annex" it's neighbor and what it believes, rightful territory, all of Ukraine... >

Which is precisely why Ukraine won't negotiate a West-friendly peace with Russia unless NATO membership is included in the deal. >

NATO membership won’t be extended to Ukraine for as long as they maintain any claims to areas occupied by Russia, as NATO doesn’t want to get sucked into a war with Russia because of those claims. >

That's not incompatible with what I said. Ukraine will not negotiate a peace with Russia that involves settling contested land disputes unless it coincides with immediate admission to NATO. This is why I don't see Ukraine having a peace deal done until Russia is purged from Crimea. Russia won't like the idea of NATO membership, but Ukraine has zero reason to accept a loss of territory.
If Russia can win this war (i.e. hold Crimea/Donbas and then push forward), then Ukraine can safely assume that peace only gives Russia enough time to prepare for the next stage of invasion. In that case, NATO protection is essential. If Russia can't win, then Ukraine has no reason to cede land to Russia AND fail to gain NATO membership for future security. 
Ukraine will either win the war and retake as much territory as they claim is disputed (Donbas + Crimea), or they will agree to a peace deal that secures them NATO membership. They know the West cannot tolerate Ukraine being absorbed into Russia, and therefore Ukraine knows that the West will want them in NATO just as much as they want to be there. >

I'm on board with just about everything you said, but whenever I think about the endgame, a couple of things always bug me.
Let's tackle that second scenario first. I really want Ukraine to restore its pre-2014 borders, but I'm just not sure how realistic that is right now. But if Ukraine keeps kicking Russia in the teeth so hard that the Kremlin acquiesces to NATO membership, would Ukrainians be okay with giving up on Crimea?
And with regard to Ukraine potentially retaking Crimea and the Donbas: that would very likely cause some sort of major escalation on Russia's part, or prolong the war by quite a bit, at the least. Do you think there's enough enthusiasm among Western leaders for that? Whether it's a war that lasts for another 2+ years or having to deal with the aftermath of Putin doing something crazy, do you think the West is up for that?
Again, I'm hoping Ukraine restores its borders, but these two things always bother me. The fact that no one really knows how Putin might react when backed into a corner and/or faced with losing "Russian" territory must keep Western leaders up at night too. How exactly do you picture either NATO membership or the liberation of Crimea playing out? >


if Ukraine keeps kicking Russia in the teeth so hard that the Kremlin acquiesces to NATO membership, would Ukrainians be okay with giving up on Crimea?

Ukraine already tried letting Russia have Crimea for peace and 2022 happened. Ukraine is going to retake its territory, which Russia signed recognition of in 1994 because Ukraine controls its sovereignty and not Russia. It's not Russia's business what Ukraine's domestic or international policy is. As long as Russia remains in Crimea it's indicated it will continue using that as a springboard into Ukraine. Within days of the coerced 'minsk protocol' its troops were already harassing Ukrainian people outside ceded Crimea.
The problem with NATO membership is two of its members, Hungary and Turkey, have become authoritarians heading towards dictatorship and purely to play to their domestic politics I think they'll thwart anything they can possibly touch. For that reason I think it's more likely (not that it's a very likely scenario) that Ukraine signs some form of new treaty agreement with friendly nations to dissuade Russia from yet another invasion attempt. >

Partially agree. While Ukraine’s territorial integrity may be something to be flexible on, the core issue with the Russian invasion is that it attempts to control Ukrainian sovereignty.
Russia wants Ukraine to guarantee it won’t join NATO and it won’t join the EU.
The problem here, is that Russia has officially created the conditions for Ukraine to want to seek membership in NATO. In fact, Russia has invaded or meddled into former Soviet Bloc countries since the collapse of the USSR. 
Which means, Ukraine was never safe to begin with. So is the expectation that Ukraine live under Russian “preferential rule” because it makes Russian oligarchs comfortable? 
This is not a acceptable arrangement from the Ukrainian perspective.
The war, in my view, wasn’t really about territorial integrity, although that matters. It’s about the sovereignty and future prosperity of Ukrainian people.
A long war might no be preferential. But Ukraine under Russian control is? How is this better? >

russia has full control over whether ukraine can join NATO. all they have to do is invade once every 14 years >

This is technically an incorrect statement but not for the reason you might think.
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I am just here to remind everyone that Ukrainian sovereignty has been under attack for roughly two decades already. The Russians have occupied Ukrainian territory for many years now, and the "conflict" has only recently escalated into a full-blown ground war. The Russians don't "need to invade every 14 years" if they've simply never left in the first place...
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It's a pretty dark reminder that many of the issues we're debating online in forums and subreddits are issues that Ukrainian leadership has been dealing with already for almost a decade. The only reason we're now REALLY talking about this is for 3 reasons:

Ukraine is a country and deserves full autonomy and freedom from Russian oppression and aggression.
Putin has threatened to use nuclear weapons.
It's adding to the already-massive refugee crisis, and A LOT of us are hearing about/meeting/seeing actual Ukrainian refugees move to our own countries (Canada for instance, for me) and it brings the war really close to home, so it affects us more than other conflicts would.

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This is also a full-blown conflict that (for the first time, really) we're seeing combat footage of REALLY up close firefights, attacks, drone footage, everything uploaded instantly to the internet right after it happens. It's a VERY new approach to uncensored war.  It's also a whole new style of warfare and it's changing the way that many organizations (like NATO) are approaching modern conflict.