Which included, but aren’t limited to: feeding alcohol to someone who had been intentionally sober, stoking emotional fires within the parents of dead children, convincing an inebriated person to commit assault and murder, and tricking Maggie into walking into his trap by telling her that someone had defaced Glenn’s grave.
Seeing as how it took him all of two-thirds of an episode to commit all the atrocities he did.
I’m still stunned that Gregory managed to stay alive between the All Out War’s conclusion and the current timeline, and I have to assume he was in some kind of heavy coma the whole time.