Again, a vote cast for Catherine the Great. Not only did she seize the throne from her rather ineffective and offensive husband, she added huge amounts of territory to Russia, considered some pretty amazing reforms for her time, was incredibly well-read for a woman, basically started the Hermitage art collection (yes, Peter I bought the first art, but Catherine was the first to be systematic about it), and was, for the most part, religiously tolerant. There is the whole area of what she did NOT manage to accomplish (freeing the serfs, turning Russia into a constitutional monarchy, etc.) but her record is, for this period, pretty remarkable.
