So far, the most difficult faction I have played (on VH/H).

Sweden, Georgia, & Dagestan invade quickly. Can manage all of this carefully, but having a weak economy and two fronts (Swedish and Ottoman) both of which have long overland distances to travel makes it difficult to deliver a KO to either prior to other nations joining in. Then, after you balance this and smack both back a good deal, you're rewarded with a war against econimcally powerful Maratha and the betrayal of Poland. Tough juggling act.