After seeing The Incredibles 2 in theaters, Andrew and I have been on a superhero movie kick. We’ve watched every Marvel and DC movie we could find at the library, so we’ve seen a lot of CGI action, a lot of digitally enhanced muscle, and a lot of…love interests.

Overall, I was impressed with how far love interests have come in recent years. We now have strong female characters like Iron Man‘s Pepper Potts, Doctor Strange‘s Christine Palmer, and Black Panther‘s Nakia—not to mention everyone’s favorite dude-in-distress, Wonder Woman‘s Steve Trevor. But there was one love interest in particular who failed to win me over: Thor‘s Jane Foster, played by Natalie Portman.

Not that this was Portman’s fault; I thought she did her best in a role that was clearly underdeveloped by the writing team. As a result, Jane Foster undermined both movies (she doesn’t appear in Ragnarok, which may explain why it’s the highest rated of the three), and she got me thinking about what makes a strong love interest. Here’s what I came up with.

A good love interest has depth.

This means he or she is not one-dimensional. In Jane Foster’s case, she’s a brilliant scientist who is devoted to her research—which is great, except that’s the only dimension her character has. Compare this to Lupita Nyong’o’s Nakia in Black Panther. Nakia is a spy working for her country, Wakanda, but there’s more to her than her job. She also has strong feelings for the main character, T’Challa, but she’s chosen to break up with him to pursue her passion for helping the world. Not to mention she has some insane martial arts skills, and she speaks Korean.

Most importantly, Nakia has conflict. Internal conflict, that is—conflict between her love for T’Challa and her personal goals, conflict between following Wakanda’s rules and doing what she feels is right. Conflict is one of the best shortcuts to character depth you have at your disposal. If you don’t have the space to fully flesh out your love interest, give her something to be conflicted over, and boom! Compelling side character.

A good love interest doesn’t compromise.

At the start of the second Thor movie, The Dark World, Jane is still a workaholic—except now, instead of being driven by the career ambitions that made her a workaholic in the first place, she’s driven to find Thor. Let me get this straight: She hung out with the guy for a few days in the first movie, then he disappeared into outer space for two years, and now she’s dedicated her life to finding him again? LAME. Your love interest should not give up some important aspect of his or her life to be with the main character.

Nakia, on the other hand, has chosen her own goals over her relationship with T’Challa at the start of the movie. At the end, she’s conflicted over the prospect of getting back together with him and losing her own freedom and passion. T’Challa persuades her to stay with him only by offering a compromise that will allow her to do both: an outreach center that she’ll get to run.

A good love interest has an active role in the plot.

The key word here is active. In The Dark World, Jane’s primary role in the plot is that she gets infected by an evil supernatural thingy (which turns out to be an Infinity Stone) that the villain is trying to get his hands on. Now Thor must get this parasite out of Jane’s body before the villain finds her and kills her. For the next hour and a half, Jane follows Thor and Loki around as they execute their plan; she doesn’t take any action herself that significantly impacts the plot.

Nakia, on the other hand, springs to action after T’Challah’s death, rescuing T’Challah’s mother and sister, stealing one of the magical plants before the villain destroys them, and going to the neighboring tribe for help. Talk about being proactive!

A good love interest is needed.

Iron Man needs Pepper to run his business. Dr. Strange needs Christine to perform surgery to save his life. Wonder Woman needs Steve to teach her how to use non-Amazonian things like revolving doors. Thor needs Jane Foster to…suck face between action scenes? I’m not buying it.

Your love interest shouldn’t serve only to make the hero look good; instead, he or she should provide some key to the hero’s success. We should feel like the main character would not have won without the support of the love interest. In Nakia’s case, the magical plant she steals from Killmonger is necessary to revive T’Challa and reclaim Wakanda.

A good love interest has agency.

Put all these things together, and you get a character with agency. When a character has no agency, it’s painfully obvious that the writer put him into the story for a single purpose: to help the main character in some way. This results in a sidekick who blindly follows the hero’s instructions without ever thinking for himself, a love interest who only shows up to give the hero something to rescue, or a villain who serves only as a mirror for the hero’s traits.

Remember: every side character, including your love interest, is the hero in her own story. She has goals. She has a moral compass that guides her decisions. She has people, objects, and ambitions that are important to her. All of these details should shine through when she is forced to make decisions. Consider what she really wants, where her loyalties lie, and what’s at stake for her personally, then allow her to make her own choice—not whatever choice is easiest for you as the writer.

The moral of the story? Make your love interest a Nakia, not a Jane.