Convicted of drunk driving causing death is very different from being a 'convicted killer'. The former is an idiot who did not think about the consequences of his actions, the latter an individual who wanted to kill someone. From the reports available he is NOT a hardened criminal, and he was a regime critic; as were the booksellers abducted from Causeway Bay in Hong Kong.
I have not criticized extradition; it is a perfectly logical and sensible procedure if carried out legally and in accordance with agreed protocols. Forced abduction, or extraordinary rendition in US terms, is simply kidnapping.
Shynkarenko was a child pornographer who was officially extradited so it is hard to see the parallel between the two cases.