3. The original Supergirl
Supergirl made both her live-action and cinematic debut in her 1984 self-titled movie. Envisioned as a spinoff of the Christopher Reeve Superman series, it starred Helen Slater as the title character. Unfortunately, it was a critical and commercial failure.
Nevertheless. Slater did a great job at bringing the Girl of Steel to life, with her warm performance carrying the movie. It was a joy to watch as Kara discovered and honed her powers, which included all the known Kryptonian abilities like super strength, speed, hearing, and breath, as well as both X-ray and heat vision, and, of course, the ability to fly.
Honestly, the scene in which she discovers her powers and how to use them might just be the best scene in the movie. It's so pure, so joyous and a great example of what Supergirl can do, and how she enjoys being able to do it.
The movie itself could have done more to highlight what she's capable of, but you can see how the Supergirl TV series was influenced by the 1984 film as its version of Kara was quite similar to this one. And what a joy this one is, even if the movie doesn't showcase her powers enough.