In Russia the most active Anti-War Movement seems to be formed out of the russian version of r/antiwork (which is there called the “Antijob” network), together with the “Feminist Anti-War Resistance” and the “Antiwar sick leave” campaign. And right now they are preparing a fund in order to organize a series of coordinated mass-strikes and resignations, maybe the strongest anti-war action yet within Russia.
Please, if you consider this important, these groups have reduced capacities right now and would immensly benefit from anyone who can donate and spread the world in their own circles, channels and networks. Also in the fight against Putin, it is my humble belief from all the groups and individuals I am following there, that they have the best chance to have an influence.
But just read their article to which I already linked to. It does a way better job than me at explaining.
Also here's an article on the Antijob group:
https://en.crimethinc.com/2022/03/21/antijob-the-russian-anarchist-labor-site-that-terrifies-the-bosses-an-interview (P.S: r/antiwork gets mentioned in the article)