Sweden invaded Russia in 1708, but fails. what would happen if Sweden defeated Russia.
It depends really on what 'defeats' means. Sweden probably could not win a long, extended war with Russia; that's a feat that's literally been done only by one people in all of history; that said, I think Sweden could force Russia to conclude a favorable peace. Some of the biggest winners might not be Sweden, whose object was really survival as a Great Power, but her allies, Poland-Lithunia and the Ottoman Empire, who sought to gain from Russia. I think Sweden would simply want to weaken Russia, in order to improve her own position; it is worth remembering that Sweden has an inherently weak position, owing to her simple relative lack of natural resources and people relative to other powers.
I am thinking, however, now, that Sweden could seize favorable concessions against Denmark-Norway, probably in the Skagerrak and Kattegat region.
They keep the area of what would be st Petersburg and a little land. They also beat up Denmark.
Have Peter the Great killed or captured at Narva (he left the siege only shortly before Charles XII showed up with his army and utterly destroyed the Russian army) in 1700. With Peter out of the picture and the Swedish army victorious you can probably get Russia to conclude a peace deal that let's Sweden keep all its eastern possessions, including what eventually became St. Petersburg. Then Sweden just has to deal with Poland and Saxony, and we know the Swedish army can handle that.
A plausible victory is that Charles XII gets his candidate on the Polish throne and gets some large indemnities. Russia becomes too preoccupied with internal matters after Peter's death to go after Sweden again soon, and without Russia, Denmark and Saxony won't attack again. Sweden loses no territory, gets an ally in Stanislaw I of Poland-Lithuania and comes out of the war as the preeminent power in Northern Europe.
IMHO a victory for Sweden is to force Russia to accept a peace that leaves Swedens eastern territories intact, so perhaps if Peter is killed the succesor accepts a status qou antebellum
The POD seems to be in 1708, so if the Swedes had handled things better, and defeated the Russians in a decisive battle at Lesnaja or nearby, let us say by having a hidden corps from the main army around that was able to take advantage of the Russian attack on the Swedish Livonian army, then things would look better, but unless the Czar is killed here, he will return with a new and better army next year, and the Swedes seem not to have a clear goal or a strategy other than defeating their enemies. King Charles XII is very irritating in this regard.Sweden invaded Russia in 1708, but fails. what would happen if Sweden defeated Russia.