Buffy the Vampire Slayer’s Faith is often considered the bad Slayer. And it’s true that Faith was the dark to Buffy’s light. As the other Chosen One, she excelled at her job — until she made a mistake. Then, Faith went very bad, very quickly.

RELATED: BUFFY THE VAMPIRE SLAYER: 5 SCARIEST EPISODES (& THE 5 FUNNIEST)

Despite all the terrible things she did, Faith eventually started working towards redemption. As a result, Faith has been on both sides of the battle against the forces of darkness. She’s done unforgivable things, but she’s also been heroic in the face of overwhelming evil. Here, are examples of both categories.

UNFORGIVABLE: STAKED THE VERY HUMAN DEPUTY MAYOR

Faith was a scrappy fighter who threw herself into battle with vampires and demons without a second thought. She’d get so absorbed that she’d see anything that came at her as a threat. Unfortunately, her tendency to lose herself in the thrill of the fight had disastrous consequences when she accidentally staked the Deputy Mayor Allan Finch, believing he was a vampire.

Of course, a stake to the heart is just as fatal to a human, and Faith quickly went into denial about what she did. Buffy wanted to tell her Watcher, Giles, about what happened, but Faith claimed she didn’t care. She then beat Buffy to the punch by pinning the act on her. It was her first step down the path towards evil.

HEROIC: OVERCAME HER FEARS TO TAKE OUT KAKISTOS

When Faith first came to Sunnydale, she claimed it was because her Watcher was on a retreat leaving her the opportunity to come to California and visit her fellow Slayer, Buffy. That turned out to be a lie, however. Faith was running from an ancient vampire named Kakistos. When she first took him on, he tore apart her Watcher and almost did the same to her.

RELATED: THE 10 MOST BRUTAL FIGHTS IN BUFFY THE VAMPIRE SLAYER, RANKED

Yet, Kakistos wasn’t willing to let his vendetta against Faith go. To her horror, he tracked her down in Sunnydale. While Faith was terrified of the vampire, she eventually overcame her fears and staked Kakistos with a four-by-four. An act of heroism that made a positive impression on Buffy.

UNFORGIVABLE: ALLIED WITH THE MAYOR

After accidentally taking out the Deputy Mayor and trying to blame Buffy for it, Giles realized Faith was in a psychologically fragile place. He attempted to handle the situation delicately. However, new Watcher Wesley Wyndham-Pryce wasn’t nearly as sensitive. He called in the Watchers Council to apprehend Faith, and a special team attacked and briefly captured her.

Traumatized by the incident and isolated from the people she trusted, Faith went to the dark side. She turned to the villainous Mayor, Richard Wilkins, offering to help him in his plans for his demonic Ascension. Faith worked as Wilkins’ enforcer. She threatened people, stole objects, and took out anyone that got in the way of the Mayor’s grand plan.

HEROIC: TURNED HERSELF IN AND ACCEPTED HER PUNISHMENT

Faith slept for eight months after Buffy put her in a coma at the end of Buffy the Vampire Slayer’s third season. Eventually, she woke up and discovered that the Mayor’s plan hadn’t come to fruition after all. What's more, the world had moved on without her. Alone and adrift again, Faith returned to her criminal ways.

RELATED: BUFFY THE VAMPIRE SLAYER: THE 10 BEST LOVE TRIANGLES, RANKED

She came to Los Angeles and carved a reign of terror through the city in just a few days. After fighting Angel and begging him to kill her, however, it was clear something had to give. Faith decided to start on the hard road to redemption. Her first act was to turn herself in for her crimes and accept her punishment by staying in prison, even though she had the ability to escape at any time.

UNFORGIVABLE: SWITCHED BODIES WITH BUFFY

When Faith woke up from her coma in the middle of Buffy’s fourth season, she discovered that the Mayor was gone and she was without allies. The Mayor made sure that didn’t mean she was without options, however. He made arrangements to ensure she’d receive a device that would let her swap bodies with anyone. And the person she chose to use it on was Buffy.

Faith quickly took over Buffy’s life, leading to a hilarious sequence in which she impersonated Buffy in her bathroom. While she actually did try to do some good in the guise of her noble counterpart, she also did the unforgivable — and brought up some serious consent issues — when she seduced Buffy’s new boyfriend who had no idea her body didn’t house his girlfriend.

HEROIC: BROKE OUT OF PRISON TO STOP ANGELUS

Faith spent several years in prison atoning for her sins. Between Buffy and Angel, she figured the world didn’t need her to protect the world from vampires and demons. At least, until Angel lost his soul during his eponymous Buffy spin-off series’ fourth season. Wesley came to report the news to Faith and ask for her assistance.

RELATED: THE 10 MOST POWERFUL DEMONS IN BUFFY THE VAMPIRE SLAYER

Faith was quick to spring into action, breaking out of prison and going to find Angelus. Of all the people in her life, Faith felt a particular loyalty to Angel. He never gave up on her even when she was at her worst. He intimately understood the pain and effort of striving for redemption. As a result, Faith’s goal wasn’t to take Angelus out, it was to make sure Angel got his soul back. Faith was so committed to ensuring Angel’s survival, she almost gave her life in the effort.

UNFORGIVABLE: TRIED TO KILL ANGEL...TWICE

Wesley, Angel and Faith on Angel

Of all the characters on Buffy, it was Angel that Faith went after most blatantly. After she started working for the Mayor in the show’s third season, Faith attempted to turn Angel into Angelus and take Buffy’s place as his girlfriend. The gambit didn’t work, however, so Faith shot him with a poisoned arrow that could only be cured with Slayer blood. Faith figured it would distract the pair while the Mayor prepared for his Ascension. Plus, it could lead to the demise of one of the two of Sunnydale's heroes, which would be a bonus in Faith's book. Things didn’t quite work out that way, though. Both Angel and Buffy survived while Faith ended up in a coma.

When Faith woke up and came to Los Angeles, she was quickly hired by Wolfram & Heart to assassinate Angel. Faith announced herself to Angel by almost shooting him in the back and causing other damage before revealing her true endgame: Getting Angel to put her out of her misery.

HEROIC: LED THE POTENTIALS WHEN BUFFY WAS KICKED OUT

Faith returned to Sunnydale in Buffy’s seventh and final season to help in the Scooby Gang’s showdown against the First Evil. She found Buffy housing a gaggle of teenage girls who were all potential Slayers — and all targets of the First. Buffy was training the Potentials in an attempt to ready them for battle. But after Buffy led the group in a disastrous fight against one of the First’s minions, the Scoobies and the Potentials lost their confidence in her and appointed Faith their new leader.

RELATED: BUFFY THE VAMPIRE SLAYER: 10 TIMES THE SHOW BROKE OUR HEARTS

It was far from the outcome either Buffy or Faith were hoping for. Faith didn’t see herself as a leader and didn’t really want the job. However, she understood she was needed, so she stepped up as best she could.

UNFORGIVABLE: TORTURED WESLEY

When Faith accepted Wolfram & Hart's contract on Angel’s life, she decided she needed bait to bring Angel to her. So she kidnapped Wesley, who had come to Los Angeles to work for the vampire with a soul.

Of course, Wesley wasn’t just used as bait. As her former Watcher, he was the symbol of her betrayal and the person who made her life take a turn for the worse. He was the perfect person to use to demonstrate just how bad she’d become. Having him at her mercy gave her plenty of time to take out her aggression on him. She mercilessly tortured Wesley for hours while Angel looked for her.

HEROIC: JOINED THE FINAL BATTLE AGAINST THE FIRST

There was a time when Faith ran from a fight if it didn’t seem like the odds were in her favor. And when it came to the First Evil and his minions, the odds seemed overwhelmingly bleak. Instead of running from the final battle with the First, though, Faith stayed and fought alongside Buffy and the Potentials, who Buffy decided to turn into full Slayers just as the battle began.

Before the showdown, Faith also reconciled with Buffy — at least to some degree. Through her actions, Faith worked towards becoming the hero her Slayer heritage intended her to be.

NEXT: BUFFY THE VAMPIRE SLAYER: 5 BEST FRIENDSHIPS (& 5 WORST)