I'll try top this. Started as Duke of Apulia, became King of Sicily. France loses Aquitaine to a Muslim Invasion, Pope calls a crusade and the Kaiser wins, receives the Kingdom of Aquitaine title. The Kaiser dies leaving his son, my son-in-law, the new Kaiser. I requested an Invasion from the Pope, got it, invaded the Holy Roman Empire and won with the help of mercenaries. Ever since the 1.07 patch, there's been a glitch with the transfer of vassals... so my son-in-law kept every single vassal because they were duke or count tier, but the King of Bohemia. He was also imprisoned because that's just what happens after the war. And you know who you can imprison without fearing rebellion? Vassal of vassals. Imprisoned every single duke, count under the King of Aquitaine, which is all of Germany and Aquitaine. Sure I have -101000 tyranny, but what are they going to do about it? So I banish my son-in-law... now all of those dukes are my vassals... and imprisoned by me still. Then I banish them. Then the counts. And I shall replace them with Normans. Welcome to the Holy Norman Empire.
First I must revoke the titles of the barons though.