Quick tip for today. I've seen some people talk about how sometimes they have trouble when running games with certain villains because they like the character too much. They think the character has a lot of mileage and could be good for the game in the longrun, which in turn makes them not want to let the PCs kill them now - even if there is no way to really plausibly save said villain.
This isn't a sign of a bad GM by the way. it happens. We all have ideas for what could happen, and no one wants to see a loved character get removed before they realize their potential. It is, however, the fate of many a villain in RPGs. Players aren't dumb. In fact, players are often incredibly genre savvy because - well - like you they watch similar movies, read similar books, and all that stuff.
However, if you think you may have that problem, may I recommend this: make your big bad someone you despise. Make it have traits you hate. Or make them in general just reprehensible. Someone that you not only don't care if they die, but you actively want the PCs to destroy. You still have to play the villain properly, sure, but having a villain be someone you want to see get wrecked can make cheering the PCs on in those important moments so much easier.
The experience is also not without its own catharsis too. Giving a villain traits or qualities you despise, or that are causing problems for you in other ways, can at least give the satisfaction of watching them get their due in a world where there are heroes - or at least people with enough strength and agency to do something about it.
it can also be fun. Plus you can make that really cool villain you love into a lieutenant, and maybe get a heel-face turn in to turn them into an anti-villain where they're not quite an ally but also not quite an enemy. Keeping them in the game, but also with tension for the players.