Real villains need dramatic exits. At least in movies, they usually get them. but a game is not a movie. You don't actually need your villains to have cinematic deaths.
There's a trend in modern roleplaying for the GM to have some elaborate death scene plotted out, with a scripted monologue for the villain, and then to play it out like some sort of cut-scene where the players don't get to do anything. (Granted, that's kind of what's happening here.)
But the game is about the players, not the villains. You don't need to have your villains die like this. Your game is not any lesser if the heroes just stab the villain and reduce them to zero hit points and they die in a bloody mess without revealing all their secrets or swearing revenge from beyond the grave.
In particular, don't feel bad if your game is more organic and moment-to-moment, rather than a scripted melodrama. That's how people have played roleplaying games for decades.
Commentary by memnarch (who has not seen the movie)
Whoa. Yeah, okay, that's a Disney Villain Death if I ever saw one. Phasma is definitely not walking this one off. No blenders at the bottom of this pit though, so the GM could still bring the character back! Maybe! Either way, Finn better move fast so he doesn't fall in as well.
What an oddly human eye that is. Okay fine, oddly human for the comic version of Phasma; Grievous at least started as an organic being. Couldn't Nute have sprung for something more extraordinary? There was no way Phasma was actually a robot in the movies though. Or the whole regular Star Wars universe for that matter. Robots and cyborgs never get to be that important unless they're always comic relief or can fill in for that role.
Anyway..... So we're down to just Hux and Kylo for the physical villains then? There's a couple of leader roles open on Team Bad Guy now, so hopefully Phasma is the last to be lost. For now anyway. I think it'd be fitting if Hux decided to lead the attack on Crait and ended up dying there. Perhaps as he rises triumphant or something goofy like that.
Transcript
General Phasma: The enemy countered from higher up and we were forced to pull back...
GM: You smashed a hole in Phasma’s helmet. She’s having trouble getting up.
General Phasma: Funny you should speak of arising from pits.
General Phasma: There is no greater pit than the yawning chasm of time.
Finn: You should conserve all that energy you put into blathering.
General Phasma: Will you shut your mouth? I didn’t ask for advice.
GM: <roll> An explosion rocks the ship. The deck around Phasma begins to give way.
[SFX]: kaboom!
General Phasma: Tell Hux... The sands of Niima are not deep enough to bury the past... or the future...
[SFX]: krack! {the deck gives way}
General Phasma: Moments... lost in time...
GM: Phasma plummets into the enveloping fireball below.
General Phasma: I silently laugh at my own cenotaph, And out of the caverns of rain,
General Phasma: Like a child from the womb, like a ghost from the tomb, I arise and unbuild it again.
Finn: And I thought I was the dramatic one.