Astrid is an Ice Queen via being both a battle-ready Action Girl and looking down on the protagonist as a useless, bumbling sap. She gets better, of course.
Toothless could count too, since he was wary of and didn't like Hiccup very much in the beginning. He eventually grew attached to Hiccup and became fiercely protective of him.
Tigress in the Kung Fu Panda series. Originally a bitter Resenter to Po who seemed to snatch away her dream of becoming the Dragon Warrior, she softens considerably after Po proves himself by defeating Tai Lung singlehandedly. By the time of Kung Fu Panda 2, she has become his closest friend among the Furious Five and perhaps even more.
EVE from WALLE initially doesn't want anything to do with WALLE, but eventually warms up and falls in love with him.
Sgt. Calhoun in Wreck-It Ralph initially only sees Felix as an unplanned tagalong, but warms up to him throughout the movie and marries him at the end.
In Frozen, Elsa is emotionally reserved and afraid of her powers throughout the majority of the film, but after Anna sacrifices her life for her sister and almost dies, she understands that The Power of Love is what's needed for her to control her powers and thaw the winter she made.
Sawyer in Cats Don't Dance was shown to be pretty frosty due to her dreams of stardom being broken and was pretty harsh around Wide-Eyed Idealist Danny. However, Danny's determination to get into movies eventually defrosted her and she became the one to have the most belief in him.
In Strange Magic both the heroine, Marianne, and the "villain", Bog, have closed themselves off due to past bad experiences with love. Over the course of the movie they defrost each other in bonding over those experiences. By the end of the movie both are willing to open themselves up to new love with each other.
Penny from Mr. Peabody & Sherman initially acts like a bully to Sherman due to his adoptive father being a dog, but eventually warms up to them while accompanying them on their time-traveling adventures.
Leia from Star Wars. Her relationship with Han Solo in The Empire Strikes Back is an example, as she starts out rather icy to him but by the end is declaring her love for him.
It is perhaps dramatically notable that they start out fighting in an ice cave, working together out of need in a foggy cave and declare their love in an industrial facility filled with jets of steam.
Many Bond girls, at least for the brief period before they melt into James' arms.
Vesper Lynd, Casino Royale (2006). Technical realities of her being a civilian, and not actual royalty, while looking down her nose at the vulgar Bond are utterly meaningless, both in the story and in this trope.
Miranda Frost in Die Another Day appears to be a straight-up version of this trope, right down to her Meaningful Name, but is actually a subversion as she's secretly working for the villain, and thus didn't 'melt emotionally' as she appeared to.
Melina Havelock of For Your Eyes Only is arguably the iciest Bond girl, with her desire to avenge her murdered parents.
X-Men: The Last Stand: It's alluded to when the Phoenix (who is presumably using her telepathy) says to Wolverine, "What, you think [the Professor's] not in your head, too? Look at you, Logan. He's tamed you." Unbeknownst to both Wolverine and the audience, he has grown to love Xavier as a friend, and this finally comes to light after Logan crumbles emotionally after Charles is murdered. This is the first time in the original trilogy where Wolverine had displayed this much vulnerability towards a male character.
X-Men: Days of Future Past: Wolverine's bond with the elderly Professor X must have grown quite strong during the Time Skip in between The Wolverine and Days of Future Past because after Logan meets the younger Charles—who is practically a stranger to him—he gradually sheds his outer "macho armor." Compared to Wolverine's normally gruff exterior (especially towards other male characters), he really is quite gentle with Xavier in a few scenes where it's just the two of them, like the plane ride to Washington D.C. and the heart-to-heart talk they share in the Alternate Timeline.
I Heart Huckabees: The character Brad first appears to be a sexy, smug, condescending corporate manipulator. However, as the film moves to its denouement, it becomes clear that Brad is desperate to be liked — and convinced that being a male Stepford Smiler is the only way he can get people to like him. By the end of the film, the defrosting has already begun.
In Blade Runner, Rachael experiences a thaw after she discovers she's a replicant. Her confusion and vulnerability make the infamous rape scene with Deckard all the more disturbing.
Back to the Future Part III, in which Doc, who in all likelihood has never been interested in a woman for all his many years due to his eccentric lifestyle and devotion to science, insists that love at first sight is a scientifically ridiculous concept - and is promptly proven wrong the moment he lays eyes on Clara.
Clint Eastwood's character in Gran Torino starts off as a racist jerk with a short fuse but gradually throughout the movie warms to his 'gook' neighbors by seeing even more reprehensible characters elsewhere in the neighborhood.
Dr. Grace from Avatar. Jake - and the audience - meet her as a cold, snarky and non-social woman. In her avatar body, though, she seems downright joyful. Of course, you'd be pissed-off too if the only way to get to the place you've been studying your whole life is because a bunch of army guys want to destroy it and its people for literal Unobtanium.
Neytiri could count as well, due to her being rather hostile toward Jake at first. She begins to warm up to him as they get to know one another, and eventually falls in love with him.
Tyler Perry makes use of this trope a lot. The heroines of Diary of a Mad Black Woman and Madea's Family Reunion, for example, have physical and sexual abuse in their backgrounds, respectively, and both require a tremendous amount of care and patience from their eventual love interests before they finally thaw.
Theodora Goes Wild: Due to Theodora's upbringing in a small town full of gossiping, Puritanical women, she's very reserved and only let's herself go while writing her daringly perverse novel, The Sinner, making her quite the ice princess. But when Michael Grant, the book designer, tries to bring her out of her shell, Theodora begins to thaw out.
Kay in Love Before Breakfast initially rejected all of Scott's advances, but eventually falls for him, and begins to thaw.
In Pride and Prejudice, both Darcy and Elizabeth are ice princesses; they go back and forth rejecting each others advances until the end of the last act where Elizabeth finally accepts Darcys hand in marriage after he proposes for a second time. Probably belongs in literature as well.
Practically the entire point of The Cutting Edge, which is about an Olympic-class female figure skater who can't find a partner because of how high her standards are and how vicious she is toward them. The guy she eventually finds actually refers to her as an ice queen in the scene right before she finally defrosts. It's so much in focus that the film even ends before we find out whether or not they won the Olympic gold medal.
Sally from Don't be Afraid of the Dark starts out as this. When she first meets her dad's new girlfriend Kim, she coldly rejects Kim's attempts at friendship with her, first shown when she hesitantly accepts the teddy bear Kim bought her. Over the course of the film, she warms up to Kim when the latter is the only one to believe her stories about the evil creatures living in the old mansion they're staying in. This is best exemplified when she's shown to be visibly upset when the creatures ruin her teddy bear, and even more so when she cries at Kim's Heroic Sacrifice near the end.
In Unaccompanied Minors, Oliver Porter starts out as being a bullyish character, irritated that his flight to Hawaii was cancelled, but having to deal with the antics of the children, he eventually calms down and actually plays Santa Claus for all the stranded children at his airport.
A strange variation where, rather than over the course of Iron Man 2, on the in-movie film reels Tony is going through, he starts to find more and more evidence that his father was not always the cold fish he remembers from his childhood. (This was paid off in the Captain America film.)
Howard Stark: Ladies and gentlemen, I'd like to show you...my ass. *turns his back on the camera and thrusts his butt out*
The emperor thinks this is what his wife is in Legend of the Black Scorpion, even telling her if she is a lump of ice, she will melt in his mouth. Averted throughout as he's wrong and he fails.
The best male example is Rick Blaine (Humphrey Bogart) in Casablanca. He affects like he doesn't care any more about Ilsa Lund when she re-enters his life; he pretends that he doesn't care about anything actually. But in the end he first professes his love for Ilsa before putting her on the plane with her husband.
Amelia Dedham of Donovan's Reef who behaves like a stereotypical rich snob from Boston upon arrival in French Polynesia, but quickly begins to defrost upon admitting her own fear of the situation and meeting some local children she quickly begins to bond with.
The titular character of Mad Max: Fury Road is a gruff man of few words, who has completely cut himself off from humanity and cares little for Furiosa and the women she's trying to protect. He speaks in grunts, shoots a pregnant woman in the leg and keeps his distance from everyone else. After spending a lot of time with the girls, he rediscovers compassion, changing his initial plan of "escape Joe's men at any cost" to "protect the women at any cost." At the end of the film, Max willingly donates his blood to save Furiosa's life and finally tells her his name.
Record of a Tenement Gentleman: A non-romantic example involving a middle-aged widow getting tasked with taking care of a homeless boy. Tone is initially very put out when Kohei gets foisted on her. She tries to ditch the boy in Chigasaki. She chastises him for wetting the bed, harshly scolds him again for eating the persimmons (which as it turns out he didn't even do), and is generally harsh and unfriendly towards Kohei. But eventually the frosty facade melts and by the end she's asking if he wants to be her son.
Office Romance: Ludmilla's character arc. She is cold and distant and serious to the point where she's nearly robotic, until Anatoly calls her "inhuman and heartless." Her formerly cold and distant manner starts cracking right around the time she bursts into tears after summoning Anatoly to her office specifically to deny that she is inhuman and heartless. It turns out that she's desperately lonely, afraid to fall in love again after a previous romance ended in heartbreak. Love tentatively blooms between her and Anatoly.
In Mortal Engines, Hester starts the film totally driven by revenge on Valentine, but starts to soften throughout the movie due to Tom's influence, saving his life after stating just a few minutes before she'd have abandoned him in a heartbeat after he refused to do the same to her. Comes to a head in the climax, where she realises how her quest to avenge her mother has made her Not So Different to the maniacal and unhinged Valentine, and chooses to live instead, escaping to be with Tom while Valentine gets crushed by the city's treads.
Olive at the beginning of Popeye is very snooty, especially towards Popeye. She starts to soften however when the two find Swee'pea and they eventually end up developing feelings for each other.
Wichita from Zombieland is quite a cold-hearted jerk to both Tallahassee and Columbus (especially the latter), robbing them twice. Slowly over time, however, she starts to warm up to Columbus by sympathizing with his failure to find a girlfriend in middle school and his family likely being dead in his hometown. By the end of the movie, she considers them close friends, even finding a Twinkie for Tallahasse.