You don't have to like it, but this is how diplomacy, high level diplomacy, works. If you want a bloody, aggressive monster to stop being a monster, you don't call them a monster, you offer them "security guarantees" (within their pre-war borders only, of course) to give them an out to stop being a monster. They then can say to their populace that this is all they wanted in the first place, no matter how much of a bloody fucking lie it is. This is not playground fairness, this is realpolitik.
And, please, I'm not saying this will work, not at all.. I'm saying that this is how the diplomatic process begins. It's an excruciatingly convoluted and internecine process full of cynicism and lies, and it IS how opposing nations deal with each other.
And I am NOT saying Ukraine should cede one inch of territory to Russia in the end. Just remember two things about war. 1. War is hell and 2. War is diplomacy by other means. War cannot go on forever if one side cannot completely vanquish the other. Diplomacy is the end game between nations, ever and always.