Prince Hans

"Oh, Anna. If only there was someone out there who loved you."

- Hans before revealing his true intentions to Anna "As thirteenth in line in my own kingdom, I didn't stand a chance. I knew, I'd have to marry into the throne somewhere. As heir, Elsa was preferable, of course, but no one was getting anywhere with her. But you... You were so desperate for love, you were willing to marry me, just like that! I figured after we married, I'd have to stage a little accident for Elsa. But then she doomed herself, and you were dumb enough to go after her. All that's left now is to... kill Elsa and bring back summer."

- Hans explaining his plan.

Prince Hans Westerguard of the Southern Isles is the hidden main antagonist of Disney's 2013 animated feature film Frozen. He is the youngest of the thirteen princes from the Southern Isles, and came to Arendelle for Elsa's coronation. Since he's the youngest in his family, he'll never be able to inherit the throne from his brothers, so he plans on usurping the throne of Arendelle. He is voiced by Santino Fontana.

Official Disney Bio
"Hans is a handsome royal from a neighboring kingdom who comes to Arendelle for Elsa’s coronation. With 12 older brothers, Hans grew up feeling practically invisible—and Anna can relate. Hans is smart, observant and chivalrous. Unlike Elsa, Hans promises he’ll never shut Anna out; he just might be the connection she’s been waiting for all these years."

Frozen
When Anna goes off to find Elsa, she leaves Hans in charge. Anna's horse runs back to Arendelle, and this leads Hans to round up some volunteers to come with him to the North Mountains to rescue Anna. After a fierce battle with Elsa's colossal bodyguard, Marshmallow, Hans succeeds in capturing Elsa. In the castle dungeon, he convinces Elsa to stop the winter, but she tells him she can't.

However, when Anna's heart is frozen and she is brought to Hans to receive a kiss from him, just before the kiss he pulls back, chuckles, and says "If only there was someone who loved you." He then reveals his true motives: Hans wooed Anna for the purpose of marrying into a royal family and becoming king, because he has no chance of inheriting the throne of the Southern Isles as thirteenth in line. Instead of saving Anna's life, he deliberately leaves her behind to freeze to death.

Hans sentences Elsa with a death charge, but Elsa's powers become strong enough for her to break out of the castle dungeon and escape. Later, when the two sisters are outside in an uncontrollable blizzard caused by Elsa, Hans confronts the queen. She asks him to take care of Anna, and Hans goes as far as to lie to her that Anna was killed by her magic. While Elsa is busy grieving her sister's death, Hans prepares to finish her by striking her with his sword when Anna leaps in front of Hans just before freezing solid to save Elsa. The recoil from hitting the frozen Anna was enough to shatter the sword and knock Hans unconscious. Anna's sacrifice also allowed Elsa to realize that it was love that could reverse her devastating ice powers and revive Anna.

Hans awakens to find that the eternal winter has ended, and is shocked when he sees Anna alive and well, since he thought her heart had been frozen. Anna walks over to Hans, and, telling him that the only frozen heart was his, feeds him a knuckle sandwich and knocks him off the boat they're standing on. Afterwards, he is put in the brig on a ship and sent back to his own kingdom to face his brothers for his behavior in Arendelle.

Personality
"The only frozen heart around here is yours."

- Princess Anna's last impression on Prince Hans. "He's a chameleon who adapts to any environment to make the other characters comfortable."

- Animator Lino DiSalvo describing Hans' character, The Art of Frozen

Hans seemed to be a brave, friendly, and noble man at first sight, asking a "weird" question to Anna about being married together. However later on in the story, Hans reveals his true self to Anna before he was about to kiss her, and is actually a fairly cruel, self-centered, and unscrupulous individual who attempted to kill Queen Elsa at the end. Notably though his affable nature was not a complete facade, as he maintained a cordial tone even after showing his true nature and also seemed to care about the men under him to a degree, though this too could have been an act.

Trivia

 * Ironically, Hans is named after Hans Christian Anderson, the author of The Snow Queen, which Frozen is based off.
 * It is possible that Hans is based on the Evil Mirror from the original Snow Queen. In the original fairy tale, it is said that those who looked into this mirror, the negative aspects of their personality would come to the surface. And that if a glass shard of this mirror got into one's body, their heart would freeze as a result of their cold nature. The mirror in the story was pivotal for it had caused one of the protagonists, Kai, to become cold towards his friend Gerda (the inspiration for Anna).
 * The possibility of this is supported by the observation that Hans, when interacting with other people, adapts aspects of that persons personality into his own. He's effectively mirroring them, making him seem more approachable to different types of people, making it easy to manipulate them.
 * When interacting with Anna he's playful, kind, and maintains a positive attitude.
 * When interacting with Elsa he's noble, generous, patient, and soft spoken.
 * When interacting with the Duke of Weselton he's demanding, rude, and harsh.
 * Another possibility of this is supported by the fact that in the end of the film, Anna tells Hans that his heart is the only frozen heart, due to how cold and manipulative he is, directly referencing the effects of the Evil Mirror had on the people who looked into it.
 * In an interview with Jennifer Lee, Lee confirms that Hans was partially based upon the concept of the evil mirror in the original story, as the original story had a lot to do with mirrors. So, as she explains, what Hans is is a mirror which appears charming to the person, but is hallow and sociopathic.
 * Hans is essentially the complete opposite reflection of many of the heroic characters in Frozen:
 * Princess Anna, for while both were shut out for many years, she actually wants to reconnect with her sister and would do anything to reconnect with her. Hans, on the other hand, was embittered by being ignored and overshadowed by his older brothers, and is willing to do anything, even treachery or murder, to gain respect and admiration.
 * Queen Elsa, for while she shuts Anna out, she does that to protect her. Hans, on the other hand, while he would never shut Anna out, he only does that so he has someone to trust, but then eventually shut her out so she can freeze to death.
 * Kristoff Bjorgman, for while very gruff and tough on the outside, he's actually kindhearted and caring on the inside. Hans, on the other hand, while being kind and friendly on the outside, is actually cruel and ruthless on the inside.
 * Olaf the Snowman, for while he represents the love between Elsa and Anna, Hans represents the breaking of Elsa and Anna's bond.
 * In an original script of Frozen, Kristoff & Hans were supposed to engage in a fight during the movie's climax. This scene was later cut off from the final draft of the movie.
 * He is the third villain in a "Disney Princess" movie not to die (the first being Lady Tremaine and Governor Ratcliffe being the second). Although Jafar did not die in the first Aladdin movie, he did in the second movie.
 * Hans bears many similarities with Gaston from Beauty and the Beast, both are handsome, both are attracted in some way to the female protagonist, both tried to woo them, both tried to kill a person close to the protagonist who is considered a monster, both lead an army & both tried to become a "hero" by killing an innocent figure.
 * Unlike Gaston, Hans does not display any signs of sexism or being a jerk prior to revealing his true colors.
 * The twist that Hans is main villain is very similar to Sentinel Prime from Transformers: Dark of the Moon, as both were introduced as tritagonists of their respective movies but then are revealed to be the main villain as the movie goes on by betraying the protagonists for their selfish desires, borrowing the minions of another villain & trying to take over a certain place.
 * Hans continues the tradition of a Disney villain who initially appears at first to be a friend, specifically Cecil Clayton and Queen La from Tarzan, Rourke from Atlantis: The Lost Empire, Stinky Pete from Toy Story 2, and Henry J. Waternoose III from Monsters, Inc, as well as other villains from different franchises such as Victor Maynott from A Monster in Paris, Sentinel Prime from Transformers: Dark of the Moon and Chester V from Cloudy with a Chance of Meatballs 2.
 * Hans bears some similarities with Alejandro Burromuerto from Total Drama, both are handsome, both are attracted in some way to the female protagonist (Anna and Bridgette), both tried to woo them, only to end up betraying them for their own selfish desires, such as Hans leaving Anna to freeze to death, while Alejandro leaves Bridgette's tounge stuck to a pole, though Alejandro had womanizing abilities toward LeShawna and Courtney (pretending to have feelings for her, such like Hans pretending to have feelings for Anna), they both receive abuse from their brothers, leading to their evil transformations.
 * Originally, people thought Duke of Weselton was the main antagonist. But it was later revealed that Hans is the real villain.
 * Hans is the seventh male Disney Villain to appear in a Disney Princess film, first being Gaston, second being Jafar, third being Governor Ratcliffe, the fourth being Shan Yu, the fifth being Dr. Facilier, and the sixth being Mor'du. Of these villains, Hans is one of several who wanted to marry the main heroine for selfish reasons.
 * Hans is the third Disney villain to be a prince, Prince John being the first and Mor'du being the second, though in the case of the latter he was a former prince.
 * Before the film was released, Hans was rumored to be Elsa's love interest, even pairing the two in many fanfictions prior to the movie's release; in the movie itself he did want to marry her and make her his consort, but he saw that she was far too collected to become his queen and so decided to go after Anna instead. He even says this himself when he is quickening Anna's curse.
 * Although not a Complete Monster, Hans, along with Lady Tremaine and Lotso (though Lotso is regarded as a complete monster compared to the other two), has become one of the most hated Disney villains ever because of his treatment towards Princess Anna and Queen Elsa and in the process crossing the Moral Event Horizon.
 * Many more are angered over what they perceive to be a "breach in Disney tradition", in which a love interest has turned out evil. Indeed, his villain song "Love is an Open Door", is tactfully disguised as a love song, further fueling this sentiment.
 * Objectively speaking, Hans is arguably one of the most sympathetic Disney villains; he was neglected by his own family for years, living in the shadow of his brothers and developing an intense psychological desire for attention and power so as to "prove" himself and validate his worth as a member of the royal family. It should also be noted that there is no indication that he would have necessarily been a bad or abusive king as far as the population at large was concerned; only his means of pursuing that goal were evil.