Must Russia (Putin) remain adamant in proving to the world its ability and last resort?
Yes, the war is inevitable especially now. You cannot simply stop a war that you just started, especially if countless lives have been already lost and the economy have taken a lot of damage. You must finish what you started, you already have shown the world your capability why stop now?
Why not that war won't be stopped in the middle of the fighting? It can be stopped if an agreement is reached just with the discussion going on to stop the Russian attacking Ukraine. In the fight between the two countries, it need to be stopped because the strength of Russia is more than Ukraine and children are being killed which is the must painful aspect of this fight.