Juri Katou of Digimon Tamers started out as a Genki Girl with a hand puppet to emphasize her childlike nature. She is the penultimate innocent of the cast, as well as the shy, sweet girl that main character Takato has a crush on. Then, once on the adventure, after a promising start as a potentially excellent Tamer, she loses her Digimon partner and gets kidnapped and impersonated by the D-Reaper, who then proceeds to use her worst memories (revealing in the process that she was a Stepford Smiler all along, completely broken after her beloved mother dies of illness and her father tries to raise her alone but can't do a lot for her) in order to feed on her sadness and use it as a justification that all humans are like her and thus had to be wiped out.
It's not quite the same as Jeri, but Keenan in Digimon Data Squad fits the bill. As a baby he falls into a gate to the Digiworld crying helplessly for hours. So he gets adopted by a Frigimon,that gets killed right in front of him via Kurata and he's only 5. So he comes to think Humans Are the Real Monsters already. But even his own compatriots don't trust him and turn on him at proper excuse. Finally his father figure Merukimon also gets killed in front of him.
Ken Ichijoji from Digimon Adventure 02. He goes from the Big Bad and Evil Genius in the first half of the season to being The Woobie and The Atoner with a Darkand Troubled Past all in one go. He deals with everything from crushing guilt to being completely isolated from everyone, to his brother's death, to being infected with the Dark Spore, to kidnapping, to being occasionally dragged into a Lovecraftian-inspired other world, to the (temporary) death of his partner Wormmon... Somebody on the writing team really wanted to make sure this guy earned his redemption.
Takeru/TK in the original series... poor TK, it just wasn't fair. At age 8 he is dealing with his parents being divorced, his Aloof Older Brother being moody and unpleasant because of this, and then he witnesses his close friend and Digimon Patamon die right in front of him without the knowledge that he'd come back okay. He does manage to deal with this and becomes a level-headed Lancer in the second season... unless he encounters anyone making use of the Powers of Darkness.
Takeru's companion, Patamon, also gets a lot of this. He is the most childlike, innocent and cute out of the main digimon, who is always looking out for Takeru, yet he easily goes through the most hardships aside from Tailmon. In the first episodes where he gets to be the main focus, he has a lot of issues with self confidence due to being the only one who cannot evolve, and even breaks down crying over this. When Ogremon and a brainwashed Leomon show up, Patamon tries to think of a plan to bring Leomon back to his senses and rescue Takeru, but is too weak to do anything and nearly gets crushed to death in the process. When Devimon is about to kill Takeru, Patamon attacks Devimon with all his might, only to realize that his attacks do nothing and, in a last desperate effort, flies in front of Takeru to shield him. This causes him to finally evolve into Angemon... Who instantly sacrifices his own life to kill Devimon. He comes back in the next episode as a baby, and then a few episodes later evolves into Tokomon. Then, as Tokomon, he gets kidnapped, beaten up and poked with sticks by a gang of Pagumon who lock him up. He gets rescued by Agumon and is reunited with Takeru... For a short while. A couple of episodes later, due to Picodevimon's influence, Takeru ends up fighting with Tokomon and abandoning him, even though Tokomon saved his life. Tokomon is left on the beach alone, depressed and nearly starving to death. After Tokomon reunites with Takeru once more, he evolves into Patamon to beat up Picodevimon and things seem to be going his way again. Then, in the movie Our War Game, Patamon participates in the fight against Diablomon and before he can evolve into Angemon, he gets attacked and beaten to near death by Diablomon. Then in Zero Two, the Digimon Emperor kidnaps Patamon and tries to put an Evil Spiral on him, and it's only thanks to Garurumon's interference that he doesn't succeed.
Everything culminates for both Takeru and Patamon in Digimon Adventure tri. movie "Confession": Patamon is the first of the eight main digimon to catch the infection and ends up biting Takeru. Takeru brings Patamon home in order to quarantine him from the other digimon. When Takeru gets home, Patamon realizes that he has been infected and, with a smile on his face, asks Takeru to kill him if he starts acting violently. Patamon tries to keep up the happy demeanor and says he has made peace with his fate in order to not make Takeru sad, but in the end they both completely break down crying. Realizing that Takeru is unable to put him down, Patamon meets with the other seven digimon and asks them to do it instead, saying that "You guys are everything I have!"
Speaking of the original series, Tailmon/Gatomon may be a badass, but that's partly because she went through this a long time ago. She was accidentally dropped in the forest as an egg when the Chosen Digimon were being transported to where they'd meet their partners, hatched and spent her entire early childhood isolated and lonely but still with a desire to be with her partner that she couldn't place, when she reached her Child/Rookie stage set off looking for her only to be captured by Vamdemon/Myotismon as a recruit for his army. She resisted for a while and ended up regularly beaten for it to the point that she gave in just to stay alive and eventually forgot the whole thing and got to be noted as one of his more valuable servants. When she does finally find Hikari and remember her past, nothing gets easier, seeing as she gets kidnapped and used to lure out her own partner and Wizarmon, her only real friend during her time under Vamdemon's service, is killed right in front of her (twice), and after Vamdemon seems to be defeated, her experiences don't entirely leave her.
Ruli from Digimon Ghost Game tends to be hit by Digimon attacks in the most egregiously gruesome ways possible. One such example is when she's reduced to a crying and screaming wreck when several Chamblemon decided to kidnap her and use to grow mushrooms that they viciously shred from her heavily mushroom-infested body. Another case much later on has her infected by a Quartzmon clone that inflicts Horror Hunger on her, driving her into a breakdown trying to eat her friends while being heavily mutated before she's rendered unconscious due to being malnourished and dragged off to be hospitalized with Mummymon. It's a wonder that it never sticks.
Other examples in Digimon Ghost Game generally involve young women being caught in the middle of a grisly Digimon attack. It happens a lot and there's no holds barred showing Digimon inflicting cute-looking young women with jarring Body Horror, or worse. Notable examples include:
A Calamaramon harassing a local island twisted the body of a very young girl into a barely recognizable spiral, rendering her immobile and writhing in pain.
An Eyesmon took over the victim of the week (a gossip-happy, stereotypical American girl) and grows eyes all over her body. She tries to remove the eyes with her hands, then with a sewing kit only for them to actually induce Eye Scream on her as if they were her real eyes and the offending Digimon to mutate her body further. She's actually scared of disintegrating once Ruli manages to alert her of her condition.
There's also a character of the week (a girl no older than Ruli) who has her brother's fiancee murdered by a Moon=Millenniumon in a lab accident. Since Moon=Millenniumon entered the body of the victim it just killed and reanimated it, her brother brought his fiancee's corpse back home and cuddled with it for 10 days while the sibling's household becomes haunted by Digimon attracted by Moon=Millenniumon's evil. It made her so uncomfortable that she called the protagonists in to investigate. To make things worse, unlike most other victims of the week, she still has to deal with a grieving brother and her fiancee's ice-cold corpse.
Hiro himself gets the full brunt of this in Episode 66, where Regulusmon baits Siriusmon into attacking him by making him think that he's now vulnerable, then seemingly slaughters him by blowing a hole in his chest through an energy beam. Seeing his Digimon partner and stepbrother seemingly dying throws the usually confident and guile Hiro straight into the Despair Event Horizon, and the face he makes afterwards suggests that he's feeling dead on the inside. He gets better on the next episode though thanks to help from Quantumon.
Video Games:
Aoi from Digimon Survive gets the full brunt of this in the Wrathful Route. Getting her best friend Saki killed in Part 9 and falling into a deep depression was only the beginning, as Renamon takes advantage of this and makes her sanity worse by using a copy of Saki to weaken her will so she would become an ideal sacrifice for the Master (so Renamon can get Miyuki out of the Master's possession), turning her into a wreck who would leave the party to mutter herself some absolutely insane things. The coup de grace happened when she stumbled into Piedmon and absentmindedly healed him in hopes of him joining her as an ally only to be repaid by beaten to near death, so she merged with Labramon into an insane monster that would kill Piedmon and attempt mass omnicide that has to be put out of her misery. And unlike most examples that happen in this series, since the events are all predetermined the moment you click the "Stay with Agumon" button to enter the Wrathful Route, you cannot save Aoi from the spiral. At all.
. Realizing that Takeru is unable to put him down, Patamon meets with the other seven digimon and asks them to do it instead, saying that "You guys are everything I have!"