You don't oppose Russia because you're an anti-imperialist, you oppose Russia because you're an imperialist.

The only people who say "Putin can end this war at any time by withdrawing" are those who deny the US empire's aggressions which led to this conflict, which is just a nonsense garbage position based on lies. They don't actually want peace, they just want victory for the empire. The real unbiased position which supports peace is wanting both Russia and the western empire to begin engaging in diplomacy, de-escalation and detente to end this war. But empire simps will call you treasonously biased if you support anything other than total Russian defeat.

This dopey propaganda-addled notion that the west did nothing wrong and Putin attacked Ukraine solely because he is evil and hates freedom actually prevents peace from happening. If one side only acknowledges the reality of the aggressions of the other side, peace is impossible. If you don't understand how a war was started and perpetuated, then you can't understand how peace can be started and perpetuated. The empire deliberately works to prevent the public from obtaining this understanding, because the empire wants war.