I'm not a genius and I'm not playing these weird head games. This isn't WWII and the Allied campaign to stop the Third Reich would never have happened if Hitler had 4,000 nukes.
We already know what would have reduced Putin's ambitions in Ukraine at any point, and would reduce them now. Three important points:
- Concession of Crimea and the Donbas
- A guarantee Ukraine never joins NATO
- Strong security guarantees
I'm sure you would call the first two of these "appeasement". Years before this war, these were the main points on the table. And after this war, they'll still be the main points on the table.
The war hasn't deterred anything.
If a peace should be negotiated, nothing will stop Putin funding contras and sorties into the rest of Ukraine, nor Ukrainian reprisals in Russia-occupied territory. Nothing except strong security guarantees. That's it.