EMERALD EMPRESS

This is the first of two Legion of Super-Heroes-affiliated villains on the list.

Why? Well, because with Mon-El and Durlans, plus various folks associated with the show suggesting in no uncertain terms that the producers hoped to get to the Legion sooner or later, we're half-expecting the season to end with him shunted to the future somehow.

This would serve a few purposes: it would introduce the Legion, give Mon-El a solid role...and mentors that aren't Supergirl, since part of the character's charm is that she's learning as she goes and so making her too much of an authority undercuts some of what makes her special.

That could give the "Karamel" shippers a little something to look forward to when Chris Wood's character comes back as a more competent hero, and a little bit more of Supergirl's equal...and it would open the door to, among others, Emerald Empress.

She's been a big player in the DC Universe of late, appearing in Justice League vs. Suicide Squad as well as in a recent story that crossed Supergirl over with Batgirl...and she's one of the most identifiable Legion villains, with a cool gimmick and a great visual.

It also helps that she's...well, a she. Supergirl's feminist message is often best served by having Kara throwing down with other intimidating women, as opposed to reinforcing the sense that the most powerful foes are almost always male. It's no coincidence that both of this season's "big bads" are women who attack Kara from different angles.

MONGUL

Mongul is definitely a character most associated with Superman rather than Supergirl, but this show has already hinted at his potential appearance a couple of times, so don't be too surprised if they come through.

After doing an interpretation of "For the Man Who Has Everything," and then mentioning Warworld and its gladiatorial arena, we half-expected to see Mongul coming along sometime this season, but we suppose that if you're going to have a badass this dangerous, he probably shouldn't be shown the door after an episode or two.

Given that we've already seen Roulette working with slavers to bring humans and earthbound aliens to the stars, it wouldn't be much of a stretch for one of these transmatter gates to bring Mongul over from Warworld, looking to find out who's messing up his supply lines.

THE TIME TRAPPER

There have been at least three different people to go by the name The Time Trapper, and all of them have been thorns in the side of the Legion of Super-Heroes.

Probably the least-notable one in many ways was the "middle" Time Trapper, the young woman named Lori Morning. As a member of the Legion, she actually had ties to the 21st Century (she was the daughter of a supervillain's henchman who ran afoul of The Atom), and for most fans, she's otherwise a pretty blank slate.

This could allow the showrunners to 1) have a female big bad, but also one who has a long history with the Legion; and 2) basically rewrite her backstory from scratch, as they did with Lar Gand and Rhea.

INTERGANG

At one point, we actually thought that the "Crossfire" episode earlier this season might be Supergirl taking on Intergang, or at least setting them up for the future. When that turned out not to be the case, though, we just kept thinking about it.

Intergang, foes to Superman, Jimmy Olsen and The Guardian during the Jack Kirby era of Jimmy Olsen comics, has shaped up to be a Lois Lane villain in many ways over the years, as her crusading investigative journalism got under the skin of the increasingly more modern mafioso and constantly jeopardized their operations.

That could actually fit in pretty nicely with Kara's reporter subplot, and of course Intergang was a major concern in Lois and Clark: The New Adventures of Superman, a series clearly pretty beloved by the writers and producers of Supergirl.

It also appeared in a major role during the recent Superman: Lois and Clark series from DC Comics, which set the stage for everything currently going on in Superman and Action Comics.

URSA

If you've got Zod and Non, people are going to wonder where Ursa went -- and as we pointed out with Emerald Empress, Supergirl's feminist message is best utilized if her best villains are also female.

Alternately, of course, they could use Faora, a similar character who has recently kicked ass in Man of Steel -- but the better option seems to be to stick with the more Donner-friendly version of the mythology, since that's something that Supergirl tends to excel at.

The only downside to this would be the one that they've already run into in the movies: how many times can your villains come from Krypton, gunning for Supergirl personally, before there's a question about how much harm she's bringing to National City? Then again, if the writers on Supergirl have shown us anything it's that they're willing to take on those kinds of questions and answer them with hope.