As for the first part of your comment, no. Being in the official military of a country is not a crime or entering into a criminal conspiracy, so if a soldier goes rogue and decides to do something they shouldn't, that's only on them. However, if a commanding officer orders a war crime, and it's carried out, then yes, everyone in the chain of command below that, and is associated with the war crime, is a war criminal. Like, say, the US pentagon ordering drone strikes on a hospital. Just trace metaphorical lines from the people that ordered it, and their subordinates, and theirs, all the way down to the people who did the actual act. Everyone that touches that tree is a war criminal. In fact, under the laws of war, soldiers have a legal duty to actively refuse any order they know to be a war crime, and it's a separate war crime to punish a soldier for refusing to commit the original war crime. "I was just following orders" is very explicitly not a defense, IIRC this was actually passed internationally after too many Nazis used that line.

Also, an official national military is a special case where most civilian laws don't apply, that's why we have military law and military courts. But the same is not said for a paramilitary organisation like the Azov.

Also, no, collective punishment is not a thing at least in US law. Individuals commit crimes, individuals get punishments. An individual would have to agree to commit a crime for it to be conspiracy.

https://federal-lawyer.com/criminal-law/criminal-conspiracy/

Federal conspiracy charges are broad and can apply to any individual who conspires with another individual to perpetuate a crime against the United States. Federal conspiracies are charged under 18 U.S.C. 371. An individual can be charged with a conspiracy to violate any kind of federal law.

you do not have to have committed the underlying offense to be guilty of conspiracy. Under the conspiracy laws in the United States, if you act in concert with another individual to perpetrate a crime, you can be held liable as well.

If they take any action in furtherance of any of the atrocities of the Azov, they could be on the hook for all the crimes, depending on the exact wording of the law in the DPR.

There's also abetting, which generally refers to calling for or encouraging the commission of a crime with the knowledge that it could result in the crime actually being committed. Given that, one, tons of Azovs are on record publicly calling for "racial purification", and it's common knowledge (certainly to the initiated members) that the Azov Battalion has actually committed acts toward that in the past and intends to continue, I think that would apply. Depending on the jurisdiction, aiding and abetting could well net you the same punishment as if you personally committed the crime, or some percentage of it.

None of this is legal advice BTW, but I think the vast majority of the Azov are on the hook for at least one serious offense.