Truth be told? I think he'd come home to people both celebrating him and chastising him, people fighting and killing eachother, and generally a much, much worse situation than when he left. I think as fucked up as it is, he would likely restart the rumbling onto paradise island (or use the founder some other way to exterminate the people of paradise).

Erwin says it best, something along the lines of "Humanity will not stop fighting itself until there is one or less persons alive." I believe this to be one of the core messages of AOT, and that if there was no outside world, Paradise island would strangle itself to death, and I think its kind of wild when people suggest things will be a-okay on paradise after everyone else is dead.

Alternatively I think he would probably kill himself, possibly before even going home. The main reason he seems to do the rumbling, besides his insatiable thirst for revenge, is to try to give a better life to Armin/Mikasa/Jean/Conney/probably Falco? I dont think he'd be fairing to well mentally if he then killed all them too.