What are some of the encounters you have put players through where they weren't supposed to win but just survive?

Every single one roll combat check.

That one meeting with a Hutt. The one time they ran from the Dark Lord and jumped directly from the atmosphere (an impossible RRRRP) in panic. Then there was this other meeting with another Hutt...

Now that I think of it: any meeting with any Hutt, actually. If, after one of those, the players don't feel coerced or conned, but happy it wasn't even worse, you did it wrong.

Well, I've some plans to have my players chased around by an ancient giant space crab. She's mostly trying to get them out of her house and won't use lethal force unless she needs to. The goal is to have her chase them through a bunch of dangerous set-pieces so they don't get any ideas about going back there. Still working out the details

I had a group of players that are making their own mercenary army. They built a space station above Rattatak and then got attacked by 3 Star Destroyers. But one of the players is a commander type and so rolled ludicrously for mass combat and ended up taking down one Star Destroyer, fleeing while the base was destroyed, dropping another one onto a second planet and evading the third. They had a second base on Lehon and had reactivated the orbital defense field that brought the second Star Destroyer crashing onto the planet. Then they surrounded and murdered all the imperials over the course of a month long siege and took the weapons and remaining vehicles from the wreckage.