It depends on what you mean by power. the N'Drangheta dominates the cocaine market. The Albanians and other Eastern European groups are involved heavily in heroin and human trafficking. Russian groups probably make the most money off of white collar fraud and they make a lot in arms trafficking along with Italian and Eastern European OC. Even the Hells Angels and other outlaw MC's are big in Germany, Holland, and Scandinavia. Do you mean who dominates their home country more than another group effects its respective country? If you want a simple answer I would say you really cannot say absolutely who is most powerful, as it is not clear cut who is because there are so many factors at work.