A peace treaty? Are Ukraine and Russia at war then? (I think they are, do you?)
Irony apart, there isn't anything like a full defeat, unconditional or conditional or any type of surrender. This is a bear trap and a nasty one.
You demand unconditional surrender from Ukraine while you argue they are not willing to negotiate. I am not sure you what type of deals have you closed in your life - usually someone concedes something and the other concedes as well so everyone is slightly unhappy with the result. In this case, by waging war, I can tell you that both sides are going to be worse off. There is no way the US and Europe are going to let Russia come better-off this war and there is no way Ukraine is going to forget. Needless to say that all the dead civilians and soldiers are not better off.
Of course, I would also prefer a quick and bloodless operation, without unnecessary casualties, destruction and bloodshed. Unfortunately, for this, Ukraine must capitulate, because Russia's policy towards Nazism is characterized by zero tolerance. Russia denounces Nazism and has strong evidence of widespread Nazism in Ukraine. There are serious documentary claims about the work of bio-laboratories in Ukraine. The contents of the bunker near Azovstal have not yet been fully disclosed, but the Azov fighters are already behaving there openly like terrorists, trying to exchange hostages for food by live weight. According to the results of the operation, there will be a court like Nuremberg 2, all those responsible will be punished. The fate of the territories of Ukraine liberated from Nazism will be decided by referendums of local residents following the Kosovo precedent. Everyone will again live a peaceful, calm life, as befits civilized Europeans.
But the biggest problem Putin will now face is not Ukraine. Finland, Sweden and Ukraine are certainly now almost forced to join NATO. Europe will take all steps to reduce or remove energy trading with Russia. Congratulations for your victory.
Scandinavians are much more adequate than Ukrainians and for the most part do not experience Russophobia. There are problems with the adequacy of politicians with a vagina who have fallen under the spell of the masculine image of NATO and make incomprehensible initiatives from which the people of Finland and Sweden are actively perplexed. So the entry of Finland and Sweden into NATO is still in question, in Finland there are debates in parliament and it seems that common sense is ready to prevail there.
Ukrainian people will pay a high price for freedom - it should have been much easier, if Russia had a decent leadership.
You can always do something better, it turns out as it turns out.