It wasn't long ago that one of your closest friends died...You mean, he was murdered. There is no single solution to defeat Putin, otherwise it would have been found long ago. Putin must be fought on the battlefield and on Russia's streets.
It is naive to think that Western sanctions and arms supplies are enough and the Russians can just sit and wait for him to fall. Putin is the greatest threat to world order since Adolf Hitler. That's why, as Churchill said back then, it takes blood, sweat, and tears. The pressure has to come from all sides. People under pressure become stressed. Stressed people make mistakes. It would be pointless to combine all opposition forces into one force. Coalitions always mean compromises, and these, in turn, require compromises on the part of one's own supporters. That may work in a parliamentary democracy, but in Russia, there are no free elections and no changes of government. The opposition members who do not belong to our camp are different people with different opinions, ideas, and goals. We are not Putin's United Russia party. We're not the opposition party.