Doubt you're gonna make the Master of suffering Yoshimune-sensei proud with an ending like this Isayama.
Edit: Honestly, this guy doesn't do things half-way. Everything always end up making sense, i'm sure everything is already there and we've missed it or we are gonna find out next chapter...
This dude is just a vigilante, they've fucked up his life so he's just trying to return the favor.
Can't wait to find out what he did to those bullies for Negishi to be so terrified.