Do you want to stop the war in Ukraine? Stop the person responsible for it.
Take Putin to The Hague (International Criminal Court)

Create a BTC-wallet on behalf of the ICC, make the information public, and start an anonymous fundraising campaign. Those brave guys who deliver Putin to The Hague will receive the collected reward.

Pros:
-- Independent wallet owner that everyone trusts (ICC)
-- Public companies will be happy to pitch in money to end the war
-- Holders of not-so-white cryptocurrencies will decide to use them for a good cause
-- International Criminal Court will finally start working with top defendant
-- The war will end

Cons:
-- There are none.