From Rags to Riches

Start at count tier or lower, end holding an empire. The cheeky route: Ayaz Alp Arslanoğlu of West-Tokharestan in 1066 - he's the Seljuk heir, so you can simply wait for (or hasten) the emperor's death and inherit your way from count to emperor in one lifetime. The long way is the classic count → duchy → kingdom → empire climb over generations; creating an empire title needs roughly 80% of its de jure land plus a pile of gold and prestige. Later expansions add the even sillier Rags to Riches to Rags to Riches if you enjoyed this arc.