Modern day Macedonia has nothing to do with classical Makedon. Modern day Macedonia has been a Bulgarian province for centuries. The modern language is Bulgarian with a few Serbian words thrown in for colour. But I digress.

When we say peak, we mean power relative to other peoples/nations of the time, right? Because it's hard to compare feudal Russia with modern day nuclear armed Russia directly.

England I would say was at its peak during Victorian times, when they ruled the seas and colonized the whole world.
Germany: World War 2
France: Napoleon
Russia: towards the end of the cold war, but they are not much worse off now
Bulgaria: the rule of Simeon 1. Not only was our territory reaching out to three seas, but we also besieged Constantinople.