To start, the EU loan deal in late 2012 and the CIA-backed coup d'etat known as "Euromaidan" in 2013, could/should have played out differently. Instead it's evident that key players like Victoria Nuland, the CIA / Imperialistic Neo-con agenda played a significant role in exacerbating tensions during that time, ultimately leading to the destabilization of the country.
Secondary, Ukraine should have ceded the eastern territories as "independent states" in 2015 post the Minsk agreements.
Those events have lead to the "special military operation" in 2022, as they disregard the clearly defined "red line" of NATO being in Ukraine which was set by Putin a long time ago.
To defuse things now though? (It's too late now, the Military industrial complex has their pound of flesh.) Have Ukraine exist freely, similar to Finland before it joined NATO. This would respect Ukraine's sovereignty and ensure its independence without it being a vassal to geopolitical alliances.