This invasion is an egregious violation of international law, and the tactics used by the Russian army have been barbaric and indiscriminate. Putin's ultimate aim is to restore the Soviet empire, even if it takes massive bloodshed and false pretexts. He must be held accountable.
NATO and the US have ignored Russia's security concerns by breaking its promise not to expand eastward in return for German reunification. These concerns are legitimate and taking them seriously would have avoided the Ukraine tragedy.
Even if war crimes have been comitted, it will be a long and difficult process to prove it and prosecute those responsible. The ICC faces the grueling task of meticulously collecting and preserving evidence from a war zone, while being fully reliant on national governments for intelligence.