If the west stopped supporting Ukraine, Ukraine would continue to fight for some time still.
The war would be over immediately.
And after a capitulation there would likely ne purges killing still more Ukrainians.
There wouldn’t.
So no, Ukraine could not end the killings tomorrow. Putin could. He chooses not to. He chooses the death of millions of Russians and Ukrainians. Because he truly does not care.
Yes it could, but you will never accept the reality so the war will keep going and people will keep dying. The blood is on the hands of war mongers such as yourself. People like you are what makes this war possible.