Supergirl (1984) (Blu-ray release 2018-7-24) was a critical and commercial failure. I have no intention to criticize the effects. The story is seriously bad – after drawing a flying insect with a stolen energy ball, Supergirl puts her home planet in danger because this insect flies. So she goes to Earth to find the ball.
The main villain is not threatening, and letting her do foolish things make it worse. The supporting villains are a complete waste of screen time. The lair of the villains is an abandoned theme park – although I suppose this is not uncommon in comics, it feels really odd in a live action movie, particularly when entertainment rides are presented as danger when they clearly are not. The love interest is dumb, and the whole romance is too shallow to carry any weight.
By looking at this failure, we can appreciate how the Supergirl TV series, and other DC superheroes TV series as well, get so many things right.