Having a vendetta as a goal to be fulfilled is a strong driving force for a character. It can provide meaning and determination to the characterisation, which makes it relatively easy to steer a path through the endless possibilities of life. Do whatever leads you closer to your goal, and do it with gusto.
Once completed, though, a person seeking vengeance can become lost, unguided. With a world full of other things to do, they don't know what to do next.
So give them some tempting options or other missions!
Commentary by memnarch (who has not seen the movie)
Oh! Well, that's better than I thought. I'd thought that Snoke was basically stuck in that chair, perpetually hunched over. His posture might suck, but he still looks more mobile than the Emperor in Episode VI now. Maybe taller as well? It's hard to tell since Kylo's kneeling on the floor, but those would be some very long legs in panel 5 if so.
Man this room is trippy. The red mood lighting and super reflective floor are still messing with my eyes. I keep looking at the device in the center of the panels and thinking it's floating in place or a thin-framed tank of some kind. It's definitely a unique idea for a throne room, but it's still a really weird aesthetic for The First Order. The dark red at least fits with some of the previous scenes, especially the first firing of the Peace Moon. The mirror polish? Not so much.
Good for Sally staying in character though. Why would Kylo or Snoke know about Allan, Jim's other character? There's probably plenty of things Allan could mess up if Jim really tried. Heck, he's already tried to get himself killed once this Episode! That'd probably require some extra thinking on his part to go further than that however, so maybe that'd be asking too much.
GM: I guess the floor is yours, Sally.
Snoke: Kylo Ren. Let’s catalogue the things I asked you to do.
Snoke: Retrieve the map to Ahch-To. Kill Rey Solo. Find Luke Amidala. Destroy the Jedi. Bring glorious peace to the Galaxy.
Snoke: So what are we? None from five?
Kylo Ren: I killed Han Solo!
Snoke: A personal vendetta, irrelevant to the big picture.
Snoke: Once he was dead you weren’t driven enough! You lost all purpose! His daughter defeated you!
Snoke: In fact, let’s call that negative one from five.
Snoke: Killing Han Solo has only made the Resistance more competent on average!