It's time to engage in that age-old tradition of arguing which superhero is stronger than the other. This time, it's teams. A-Force, the first all-female Avengers squad, and the Legion of Super-Heroes, an assortment of people from all over time, space, and continuity (but mostly the 30th century).
Each team collectively packs a punch, and some of their individual members count among the most powerful characters in their respective universes. But who would win in a straight-up fight? It might be either, but let's take a look at the characters who would tip the scales in a battle royale between the two teams.
10 Legion of Super-Heroes: Mon-El
Mon-El is one of the strongest Legionaries in any incarnation. As a Daxamite, his powers are essentially the same as Superman and Supergirl: heat vision, super speed, strength, and stamina (amongst many other things). What separates him from them is his vulnerability to lead. Whereas the Kryptonians lose their advantage with Kryptonite, it's a far less common substance than lead, which anybody in the A-Force would be able to leverage (Singularity could teleport him to a lead universe) and it would be over quick.
9 A-Force: Singularity
Speaking of teleporting to another dimension, Singularity would make life very hard on Mon-El and his entire team. She is in large measure responsible for the formation of A-Team, bringing them together when she crashed into Battle World during the events of Secret Wars. She would be in large measure responsible for the end of the Legion of Super-Heroes. She can teleport people and objects between realities with no discernible limit on her power, meaning the Legion would end up in a black hole in a hurry.
8 Legion of Super-Heroes: Andromeda
Created in some way to fill in the gap retconning Supergirl out of continuity left (which, why did they do it!), Andromeda is similar to Kara Zor-El in a lot of ways. Like her fellow Daxamite Mon-El, Andromeda possesses all the firepower of her Kryptonian cousins. Laurel Gand is also susceptible to lead poisoning and requires the ingestion of a special serum invented by Brainiac 5 to survive. Still, her strength, speed, and stamina make her a formidable opponent in any battle and teamed up with Mon-El, Supergirl and Superboy, she creates a line of defense that would be virtually impossible to penetrate.
7 A-Force: She-Hulk
That line of defense would be impenetrable for most people. Jennifer Walters is not most people. She's one of the strongest people in the Marvel Universe - potentially the strongest, depending on how angry she gets. And she doesn't have any issues with lead, Kryptonite, or really anything else.
Unlike her cousin Bruce Banner (usually), Jennifer doesn't lose any of her considerable intelligence when she transforms into the She-Hulk, meaning not only is she going to punch you out, she's probably going to figure you out. Good luck with that.
6 Legion of Super-Heroes: Brainiac 5
Someone with the intelligence to rival She-Hulk - and whoever else is on tap - is Brainiac 5. A genius-level intellect, he certainly would formulate a battle plan to negate the advantages of A-Force as best he could. As a shapeshifter, he would create havoc among their ranks. He's also a brilliant inventor, so the chances are he would conjure up some equipment to try and nullify A-Force. It would have to be some of the best inventions of all-time, considering they'd get little chance to use them.
5 A-Force: Captain Marvel
The fact that Carol Danvers is in the middle of this list tells you everything you need to know about the firepower on both sides. Captain Marvel is one of the most powerful people in all the Marvel Universe and matches up very well against the best of the best in the DC universe. She can fly, fire energy beams, take a punch like nobody's business and on top of all that, she can manipulate energy and matter around her. And as if that wasn't enough, she might even be able to create illusions.
4 Legion of Super-Heroes: Supergirl
No matter what version of Supergirl showed up to fight, the A-Force would be in a world of hurt. Kara Zor-El possesses all the power of her cousin, Kal-El and that makes her one of the strongest combatants in this hypothetical matchup. Invulnerable, ridiculously strong, super fast, equipped with X-ray vision and freeze breath, Kara has only one weakness: Kryptonite. Her defenselessness against green objects would quickly become a liability, especially in the hands of someone as strong as she is.
3 A-Force: Phoenix
There are theoretically no limits on the powers of Jean Grey when she employs the Phoenix Force. An Omega-Level mutant supplemented with the incomprehensible potential of a cosmic entity, she begins and ends the conversation before the Legionaries have said a word.
Telepathic, telekinetic, and oh yeah, she doesn't stay dead, Jean Grey tips the scale of any battle toward her in a profound way. Saturn Girl can manipulate people, but Jean can possess and confuse people on a scale that Saturn Girl likely would not even be able to comprehend.
2 Legion of Super-Heroes: Saturn Girl
Saturn Girl hails from Titan, the moon of Saturn (makes sense) and she is one of the most potent telepaths in the DC universe - or any universe. Things vary for Irma based on what version you're talking about (there have been some, um, revisions at DC) but in a nutshell, she joined the Science Police of the United Planets in the 30th century. She can read minds, manipulate them and unfortunately for A-Force, alter their thinking; she's taken control of some of her own teammates before, including powerhouses like Mon-El. With Saturn Girl in control of some of A-Force's biggest hitters, it's game over.
1 A-Force: Scarlet Witch
You have one shot. You have all the power of the Legion of Super-Heroes, all the intelligence, all the technology, and you have to bring it to bear before Wanda Maximoff says a single word. Good luck. With a simple phrase, the Scarlet Witch can extinguish entire races and rewrite reality. She hands down wins any fight she's in if she wants to. The only thing holding her back is herself, and that's a considerable restraint given her experience.
But if it comes down to it, the Legion vanishes without a trace. Kind of like most of their pre-Criss history.