Yes, Russia has been corrupt for a long time. Although the politics have shifted throughout the course of the many regime changes in Russia over the years, one thing that has remained constant is the prevalence of corruption in Russian government and politics. The assassination of the Russian official is just the latest indicator of this corruption.
I feel like all of my life people have been alluding to corruption in Russia. It seems they are always in the news in some form or another, especially recently. Historically there have been many accounts of corruption. Sadly, I fear that tradition will follow for generations to come unless something can be done.
Russia still has a great deal of influence from the former U.S.S.R. In Russia, anyone can die if it is for the good of the mother country. Individual rights do not really exist. Instead, it is all about what is supposedly the best for the greater good. For this reason, corruption abounds.
Russian as a whole may be corrupt. Russia probably is not not advancing international stability by assisting Syria. However, neither of those things are a justification for the assassination of the Russian Ambassador. The query seems to posit that the shooting the Ambassador is indicative of the corruption of Russia. The assassination is not evidence of such.