Storybrooke's most important hero is in a very dark place as Once Upon a Time heads into its season finale on Sunday.

Regina (Lana Parrilla) is still coping with grief after Robin Hood (Sean Maguire) was murdered in the show's penultimate episode last week, but she's still the best asset Storybrooke has to prevent Rumpelstiltskin's (Robert Carlyle) evil plan. Townspeople are quick to remind Regina that she was once the Evil Queen and express the fear that Robin's death might lead to an evil relapse — but in reality, her experience as the Evil Queen is what makes her the most powerful hero they have.

"I think she's really in a state of shock and confusion. She's been heartbroken. She's just lost the love of her life," Parrilla tells TVGuide.com. "[Regina] is kind of like, 'Give me a little credit. I think I've proven to be a kind of woman who has been making selfless choices and decisions — who has been on this path of redemption for the last couple seasons.'"

Lana Parrilla, <em>Once Upon a Time</em>Lana Parrilla, Once Upon a Time

She's not wrong, either. Last season, Regina could have pulled an Evil Queen move and killed Marian (Christie Laing) to clear her path to Robin, but instead she let her true love go. Regina also kept the darkness at bay when Marian turned out to be her own evil sister Zelena (Rebecca Mader) using a glamour spell in order to seduce Robin and become pregnant with his child.

No one would have blamed Regina for finally ending Zelena, but instead she was eventually able to use her own experiences as a villain to empathize with her sister and bring the Wicked Witch into the light as well. Now Storybrooke can count two of the fairy tale realm's most powerful villains as part of their defense team. Not even Snow White (Ginnifer Goodwin) could pull that off.

"I think if anyone were afraid of [Regina] reverting, she's taking that quite personally, and taking it as an insult because the other characters are not focusing on her progression and all the good that she has done," Parrilla says. "So I think she less fears that she's going to revert and the thoughts of others are not a concern for herself."

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Emma (Jennifer Morrison) and the rest of Storybrooke would be much better off embracing Regina's dark side because it's what makes her the most likely to be able to take down Gold when the time comes. In the height of Regina's evil reign, she ripped out the heart of her own father to exact her revenge against Snow White. It was what made her such a delicious villain, and it's also what makes her unique amongst her new hero family.

Regina understands that what is necessary is not always pretty, and thus she's the one most willing to do the dirty work required to keep Storybrooke safe. When Emma turned into the Dark One earlier this season, it was Regina everyone trusted to kill her if the darkness couldn't be removed. Regina may be flawed, but her ability to overcome her own darkness and channel those impulses into good is what has made her one of the most developed characters in the entire show.

"Living with these impulses, for her, is a very trying thing because she is trying to stay on the path of good versus evil. Yet, she is feeling these impulses inside of her and doesn't really know what to do with them," Parrilla says. "I really believe she's just in a state of confusion and I think it's going to take some time before she's figures out how to deal with them."

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Regina has more than earned the time to figure herself out, but she may not be able to have it as Gold begins his latest ploy for power. Luckily, even though Emma is one of the first to doubt whether Regina can control herself in the wake of Robin's death, she may also be the first to truly understand how important Regina is to the family and to Storybrooke. "There's this really nice thing between Emma and Regina - I like to call it the confessional scene. You learn a lot about what's going on with Regina and her identity crisis - this sort of internal conflict that she's going through right now," Parrilla says.

The truth is Regina doesn't need Storybrooke's doubts, she needs their support. She may have been the Evil Queen, but over the course of four seasons she's proved multiple times that she's selfless, empathetic and willing to do whatever is necessary to keep their town safe. It's time the people of Storybrooke started to believe in her as much as they believe in Emma and Snow White because she's given up more for them than anyone else.

Once Upon a Time's season finale airs Sunday at 7/6c on ABC.