Rei was not happy when she learnt that Shinji and Asuka were together now. She was incredibly jealous of Asuka and refused to believe the German woman cared for Shinji.
Jinnai was absolutely livid when he learnt that Asuka was enthusiastically having sex with Shinji in a daily basis after being a cold fish with him for two years. His jealousy was born from sheer wounded ego and possessiveness since Asuka was nothing but a not-quite-willing toy to him, and he never cared for her in the slightest.
Advice And Trust: Asuka is very possessive of Shinji. She constantly states that he is hers and she is not sharing him or giving him up for nothing. Coincidentally all her female classmates have crushes on him and have simultaneously decided trying to seduce him, and their attempts to flirt with and hit on him drive her homicidally mad.
Asuka at the beginning got agitated, angry and jealous when she saw her crush Kaji flirting with Misato. Later she got jealous over Shinji.
Rei was usually calm, but she could get very jealous where Shinji was concerned. When she saw Asuka clinging to Shinji's arm in chapter 5, she actually growled. While she glared silently at Asuka, her clenched fists shook, her eyes seemed to glow for a second and her friends got very, very scared.
"For such a dweeb, that Ikari's got chicks all around him, huh?" asked Touji. Kensuke nodded, still videotaping. Suddenly, his camera died. They heard a growl. It wasn't just your ordinary growl, from a dog or a wolf. This was a deep growl, the sort of growl that suggested monstrous origins, dark and shadowy nights, and the promise of endless hours of pain. It was accompanied by a blast of cold running down their spines. The two turned around, slowly. Rei was staring at Asuka, intensely, her face twisted in anger. Her fists were clenched, shaking slightly. It was hard to tell in the sunlight, but they thought they saw her blood red eyes glow brightly for a moment. "Ohshit," whispered Touji. "She's mad."
Doing It Right This Time: When Asuka suspects Rei can be in love with Shinji she starts to feel jealous… and then she stops herself, remembering her jealousy was used to turn her into a puppet and she is done with that.
Asuka had only ever seen that smile once, directed at Shinji after Ritsuko -or Misato- finally got him back out of Unit-01. Now she wasn't continually seeing red and green both at once, she had to admit it was quite a nice smile. Rather cute, in fact. Then Asuka had to fight down a sudden stab of fear, anger and jealousy. Was it possible that Rei's feelings for Shinji were...?? Arrrrgh. No, bad brain. No hedgehog impressions; that was where it all went wrong the first time round. Rei? Ayanami had deserved better than that, much less Rei Akagi.
HERZ: Asuka is very jealous. When Shinji is out of her sight she often gets tense and angry, thinking some woman will try to steal him or maybe he will fool around. Despite the protestations of Kensuke, she is hardly paranoid, since there is a woman is always trying to steal him.
A while before Asuka and Shinjigot together the thought of other women getting near Shinji was enough to get her mad. A while later, when they were already engaged, Mari realized and flirted with Shinji exclusively because she loved messing with Asuka. Needless to say, Asuka was NOT amused.
Saburo was jealous of Rei because Kaworu a long time for her bedside when she fell into a coma. He dumped Kaworu in a fit of jealousy, but when Kaworu and Rei started to hang together his jealousy increased and he started to lash out at Rei.
Except, as it turns out, she never cared about that — she was, however, jealous of Rarity's relationship with Razorwing, and tried to get them to break up so she could have Rarity for herself. This backfired horribly, and ended up leading to her friendship with Rarity falling apart.
In the My Little Pony: Friendship Is Magic fanfic A Delicate Balance, Fluttershy isn't at all happy that Twilight's infatuation with Applejack means that they can't spend as much time together. Fluttershy being Fluttershy, she feels awful about the fact that she's putting her own feelings before Twilight's and tries to be supportive of Twilight's relationship anyway.
Sakura in A Growing Affection is none too happy that Naruto moved on and started dating Hinata. She does admit to Lee, however, that it might be that Laser-Guided Karma finally caught up to her.
(bitterly) "It's funny. He (Naruto) used to like me but I was so busy trying to get Sasuke and he made me miserable. Now I like him but Naruto is with Hinata and they're happy."
Grimlock in the Transformers fanfic A Child Shall Lead Them. He is not happy when fellow Dinobot, Swoop, ends up getting the Matrix and becoming leader of the Autobots, the position he's always coveted. He gets better and ends up serving as a mentor figure to his teammate.
Kakashi calls Sasuke out on this in Legacy Of The Rasengan:Naruto. Despite knowing about Naruto's life Sasuke is jealous of Naruto's power. Kakashi points out that A) Sasuke is being very childish (because Naruto has something he doesn't), B) Sasuke knows for a fact Naruto only uses the Kyuubi's charka as a last resort and C) because of B, Naruto works and trains harder than anyone in his age group going so far as to be a Combat Pragmatist and Obfuscating Stupidity to get the drop on people.
Hefty is this to Empath in Empath: The Luckiest Smurf, especially when it comes to Smurfette, who passed over Hefty when he originally proposed marriage to her along with his fellow Smurfs because she couldn't decide which Smurf she loved the most at the time.
Trixie herself has jealousy as one of her main character flaws in this verse. In the original fic, she shows jealousy over Twilight's close relationship with Shining Armor compared to her relationship with her elder sister and in Perfect Companions she becomes jealous of the rest of the mane six having pets when she doesn't. She also shows jealousy of Twilight getting to perform in front of Celestia and the Saddle Arabian delegates. However, she has a lot better control over it than she used to before her Heel–Face Turnor her insane sister has and doesn't allow it to override her loyalty to her new friends.
The source of Daryan's abuse of Klavier in Dirty Sympathy: Daryan was originally their band's singer and frontman before their label made them switch. The switch became permanent when it was proved that Klavier had better stage presence and better vocal range.
Robin becomes jealous of Sumia in Pretender for having Chrom's love and for being married to him. Although he feels very bad that he does and overcompensates by making sure Sumia is well protected in the battle field.
Sumia is jealous of Robin for taking all of Chrom's attention despite them being recently married and Sumia about to give birth to their first child. She knows that Robin has feelings for Chrom and Chrom keeps trying to get Robin's attention.
Chrom become jealous of Frederick for seemingly taking his place as Robin's closest friend when Robin starts to become distant when he moves out of Ylissean palace after Sumia and Chrom's marriage.
In Graduate Meeting Of Mutual Killing, Ginchiyo was jealous of her sister for receiving the credit and fame for their work. This led her to try to usurp the invitation to Hope's Peak, but when it's revealed it was meant for both of them, she goes back home to tell her sister. The consequences were much more drastic than what she expected.
Alistair has a few moments of this throughout Shadow And Rose, during the period when he Cannot Spit It Out how he feels about the Warden. It mostly just makes him grumpy when Bann Teagan flirts with her, although when Zevran comes along and makes more direct offers, he becomes almost murderous.
In The Witch of the Everfree, from the moment that Sunset Shimmer met Cadance, she resented her for having been adopted by Celestia, which Sunset wanted to happen to her.
Cadance, meanwhile, was jealous of Sunset for her closeness to Celestia; while Cadance was the one Celestia had officially adopted, Sunset was the one she spent all her time with.
The titular Magma Grunt of Dating A Team Magma Grunt is not necessarily "possessive" of Brendan, but is awfully quick to get all suspicious when she sees the latter conversing with his friend May. This quickly gets cast aside however.
Subverted with her meeting of Lilia who is already on friendly terms with Brendan. It looks this way at first until she shows she's just incredibly tense from working up the nerve to ask for Lilia's autograph.
In Thousand Shinji, both Asuka and Rei were very, very jealous. Asuka got mad when Rei flirted with Shinji, and Rei was furious with Asuka because she made Shinji happy and refused to share.
Asuka in The Second Try is pretty jealous. She strongly disliked Kaworu, partially because he lusted after Shinji. She didn't like Rei either because Shinji had strong feelings towards her, but she stopped being jealous of Rei because she realized that the blue-haired girl wasn’t a threat.
Neon Genesis Evangelion Genocide: Asuka doesn't like when other girls get too close to Shinji. She resented Rei because she thought Shinji would rather being with her.