The largest extent of the Russian Empire was certainly 1945-1989 when it included the USSR and virtually all of Eastern Europe behind the Iron Curtain, and of course Putin was personally involved in that.

I don't think that Imperial Russia's contest with the Ottoman and British Empires over SW Asia in the Great Game can be overstated, nor the fact that they fended off Napoleon (Russian troops marched through Paris.) and the Germans twice, the second time in the biggest military campaign in the history of the world. The Russians weren't just conquering hapless tribes people, and in fact Circassians were sought after by the Ottoman Sultan as his elite troops, the Mamluks. War will always be in the picture for the Russians.