The best ways to stop war are:
1. Set up a committee for the both sides of the war plus a neutral committee
2. Call the two parties for a dialogue
3. Settle the immediate and remote causes of the war.
With these I believe war can be called to a resolution stage.
Ukraine and Russia have been doing that.
But still, there seems to be no sign of these two calling for unity and stopping the war as soon as possible. Both of them won't go low with their ego and will still to continue beat and defeat each of them.
In the first week, they've been having peace talks but it didn't do. The only thing that will solve this war is for Ukraine to surrender and that would be peace for both of them. We know that Russia won't stop even with economic sanctions. It's actually hard to maintain balance for these if we're thinking about it.