These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Star Wars: Rebellion
Game Breaker: The Bulwark-class battlecruiser and TIE Defender are the two main examples. Early on, the Alliance Escort Carrier is a good example too.
Capturing Vader or Luke can be this because they have insanely high Combat statistics that only get higher with time.
Also, if you're a Rebel, any battle in the shadow of a Death Star, complete with Death Star shields, and a pretty sizable fleet — with a lot of TIE Defenders, of course — and Interdictors. Yeah, you can say good-bye to that fleet. If it's all around Coruscant, you need to do it to win the game.