Is it a bird? Is it a plane? No, it's Supergirl!
One of DC Comics' most underrated superheroes, Kara Zor-El is Kryptonian like her cousin Superman, and also arrives on Earth with a destiny of becoming one of its protectors. She lives up to that destiny well, taking flight as the Girl of Steel and battling any and all threats that cross her path.
While Supergirl herself has become more of a household name in recent years due to TV and film adaptations, what isn't quite as well-known is the fact that she's actually stronger than Superman. Of course, it all depends on the story that is being told, but the belief is that since Kara is older than Kal-El, her cells are more mature and thus can absorb more solar radiation from Earth's yellow sun, making her more naturally powerful. She's also known for holding back less than he does, which means she hits much harder.
Speaking of Supergirl's strength, we have seen her showcase it in quite a few live-action adaptations since her comic book debut in 1959. She'll get to do it all again in the DC Universe's upcoming movie Supergirl: Woman of Tomorrow. As we anticipate her return to the silver screen, let's take this opportunity to look back her movie and TV appearances thus far and figure out which Girl of Steel is the strongest of them all.