Because the first two series weren't depressing enough...
Heavy spoilers below; look at your own risk.
* Guilmon's first evolution to Growlmon - it was everything Takato imagined, GoneHorriblyRight. For a short moment he becomes scared that Guilmon's now a monster and doesn't remember him, and then a little voice pipes up.
--> "Takato? Why are you crying, Takato?"
* Impmon trying to hug Ai and Mako when The Dog Deva, Caturamon, tricks him into thinking he was back at their house. And then watching his heart sink as he sees Ai and Mako fighting over a new puppy just like they did with him...
* Leomon's attempt to stop Beelzemon, who saw that Beelzemon wasn't truly evil, but misguided. "To have power is not to be strong", then looking at Jeri reassuring her what their bond means to him. He is then impaled by Beelzemon, and Leomon can only ask why Beelzemon can't see any other way.
** Beelzemon's final response to Leomon: "You're wrong, to have power is to be strong". The way of life that many digimon are forced to believe in order to survive in Digimon Tamers. Digimon that can have good lives are redirected by the might equals right concept, spending their lives fighting each other and absorbing data.
* Jeri pleading Gallantmon not to kill Beelzemon in revenge:
-->"B-but if you kill him, we will not be able to revive Leomon, why can't you see that?! I... I just don't want anyone else to die! It's too sad... Please...!"
** The English dub is, if anything, even more painful because we start to see Jeri's cheerful facade crumble and her inner loneliness and lack of self-worth break through...
---> '''Beelzemon''': I don't get it, why are you protecting me? I destroyed your partner
--->'''Jeri''': I hate you for doing that! But even if you died it wouldn't bring Leomon back. It's my fault he's gone, and if you destroyed each other that would be my fault too. I just can't let anyone else... get hurt... because of me...
* After reverting from their first Ultimate evolution, Takato hugging Guilmon and telling him that they'll always be together, no matter what. If you know what happens in the end...
* All of Jeri's descent into madness and possession is insanely powerful even in the dubs, equal parts terrifying and lip wibblies. Parent death? Check. ParentalAbandonment? Check. Revelation that she's been screaming on the inside for a long time and slowly getting worse for ''the entire series''? Check-a-roony! [[TheWoobie Poor little girl]]!
** Later, we get to see that Mr. Katou was not the aloof JerkAss [[JerkWithAHeartOfGold we've been lead to believe he was]], but actually [[ParentsAsPeople a normal guy who utterly failed to deal with raising his girl alone after his wife died]]. Once he realises [[ItsAllMyFault it's all his fault]], he tries to rescue Jeri from the BigBad [[FoeTossingCharge on his own]] by crashing a van on the D-Reaper, tearfully [[IKnowYouAreInThereSomewhereFight attempts to talk her out]] of her MindControl only to see Jeri's too emotionally damaged to hear him, and almost gets killed by the EldritchAbomination holding her hostage.
* When Takato confesses his feelings to Jeri, not realizing yet that it's not really Jeri he's talking to.
** What makes this even more heartwrenching is Takato revealing that he feels responsible for everything that's happened, including Leomon's death and Jeri's descent into depression, and apologizing to "Jeri" and practically begging her to just talk to him.
*** And then Jeri starts to just [[CreepyMonotone emotionlessly list off]] the nutritional information on her meal, completely oblivious to Takato's anguished pleas, it's equal parts heartbreaking and creepy as all hell...
* Beelzemon's entire character once he becomes TheAtoner. This change leads to one of the season's greatest [[CrowningMomentOfAwesome Crowning Moments of Awesome]], followed immediately by one of its biggest Tear Jerkers when Beelzemon uses everything he has to [[FoeTossingCharge smash through]] the D-Reaper's defenses, only to be stopped just before he can reach Jeri. [[NormallyIWouldBeDeadNow Severely injured]], his wings shredded, his [[WaveMotionGun weapon]] lost, all out of options, he manages to summon up the attack of her Digimon Leomon's Fist of the Beast King, in a MyNameIsInigoMontoya moment. Not only does he punch through the D-reaper's defenses to Jeri, but hearing him say the attack, and hearing the attack itself, snaps Jeri out of her HeroicBSOD. [[HopeSpot Just long enough for Beelzemon to yell at her to give him her hand.]] Jeri looks up, expecting Leomon. Sees the digimon that killed him instead. She's so traumatised that she '''can't''' move, and the D-Reaper closes the wound. Beelzemon gets impaled from behind by flying polygons of death. Fatally wounded, Beelzemon plummets to the ground, [[DisappearsIntoLight flickering in and out of existence]]. And what he says during all of this?
--> '''Beelzemon''': "Jeri! Take my hand! Take it! Jeri! Jeri! Just let me save you! I ''need'' to save you! Jeri! I just need one more chance! ''Just give me one more chance!''"
---> '''Jeri''': You're... you're not Leomon...
** In the Japanese dub the scene is, for the most part silent besides the character's as the music score stops playing. This is powerful and effective, but no where near as emotionally manipulating as the score that plays during this scene in the English dub and it cements this scene as one of the English Dubs finest moments.
** In the manga version of that scene, she actually ''does'' accept Beelzebumon's attempt to help and approaches, but he is cut down before she can take his hand.
** How he screams "I need to save you!" on the verge of tears... even though he called his own past actions "unforgivable" he still puts everything he has into trying to rescue her at the repeated risk of his own life is what being TheAtoner is about. Thankfully, Jeri does accept him in the end, and the reconciliation between the two is a tearjerking moment in itself.
** When Ai and Makoto, having seen the whole thing on TV, take shelter with him. Those two little kids--who are even younger than Suzie, try to reassure him he did great, fighting out there, while he insists he's failed and is going to die. Then they tell him not to....
** "You're not Leomon..." You can just feel Beelzemon's heart shatter when Jeri says it.
*** You can actually see it in his eyes.
** And then there's the Tamers horrified reactions when the D-Reaper stabs him. Gallantmon and Sakuyamon both give a BigNO and move to save him, but the D-Reaper blocks them off, either restraining them or slowing them down enough that they can't reach Beelzemon in time. They can both do nothing but watch as someone who, despite all odds, has become their ''friend'', falls to his death.
* Shortly before the above scene, the D-Reaper decides to give him a BreakingSpeech reminding him of all his crimes ([[BeAllMySinsRemembered as if]] [[TheAtoner he could forget]]) ...using Jeri's voice. The change in his posture from defiant and angry to despairing and guilt-ridden as it hits home is particularly heart-wrenching.
-->'''D-Reaper:''' Analysis complete. Subject positively identified as Beelzemon. Beelzemon: the Digimon that tried to hurt Jeri Katou and other human children in the Digital World. Beelzemon: the Digimon that destroyed Leomon. Destroyed Leomon. Destroyed Leomon. Destroyed Leomon. Destroyed Leomon.
** And of course there's his ''verbal'' reaction to it, too.
--->'''Beelzemon:''' Stop it! Stop it, stop, stop it, ''stop using Jeri's voice!''
* It's PlayedForLaughs at first, but the part where Impmon is trying to get someone, anyone to tell him what the note Ai and Mako left him says. And then when Jiànliáng's martial arts instructor reads it out to him. In light of what's happened and what will happen, you can't help but feel your heart swelling.
--> '''Impmon''': How come you're not scared of me?
--> '''Chou-sensei''': The body is nothing more than a container. At the very least, I didn't feel an evil heart within you.
* Really, the final episode of Tamers from about 4 minutes to about 4 seconds before the ending credits was a TearJerker. Watching the Tamer's partners de-digivolve and then disappear into the Digital World, Henry's father's guilt-ridden reaction as he reveals ''why'' they're going away, yet Jianglian still manages to smile at him and then Mr. Lee weeps, and Takato thinking that he'll never be able to keep his promise to Guilmon.
** Sadly, if the actual canon is to be believed, the opening that Takato found turned out to be too small for them to actual reunite with their Digimon partners, there is a Firewall keeping humans out of the Digital World that cannot be cracked (without possibly destroying the world), and as of a year after the series ended, the Digimon and their Tamers have not reunited, the closest they get as of this point (the last canon release in this series) was being able to send messages to their Digimon. Talk about a downer.
*** Which may not even be ''official'' canon. Even one of the show's creators has since stated that they like (perhaps even prefer) the "Runaway Locomon" movie and its implication of a reunion, the audio drama has not been expanded upon... Even then, if you consider that it is canon, this doesn't totally mean a solution won't ever be found. But more importantly, it's much easier to end with the HopeSpot that is the ''show's'' final moments, because it seems to be closer to what the writers intended rather than the audio drama (so still quite sad, but not soul-crushingly depressing at least).
** To make it worse, compare the endings of ''Adventure'' & ''Adventure 02'' - In the original series, the [=DigiDestined=] were separated from their Digimon, but they at least got to give heartfelt goodbyes to one another & the series ultimately ends on Tai stating his belief that they'll see each other again; & ''02'' paid that off by having the characters EarnYourHappyEnding with the [=DigiDestined=] old & new keeping their partners. ''Tamers''? The Digimon are literally ripped from their partner's arms, after being forced to de-Digivolve, and sent back to the Digital World.
** It's really sad for Ai and Makoto. They apologise to Impmon, he forgives them and they can be a family again, and right after that? He has to leave, and being so young, they probably don't fully understand why.
* ''Anime/DigimonTamers''' movie had one during the final battle. Shisamon has reverted to Labramon, who resembles Mei, the puppy that used to belong to the little girl the Tamers are all trying to protect. She doesn't know him until he says her name, and maybe ten minutes later, he dies in order to take down the movie's villain as she screams his name and cries.
* Let's not forget the musical number from the dub version of "Runaway Locomon"
--> Promise that you'll stay for the sunset. And when the moon shines through the darkness, we can find the path that leads us home, and on the way you'll, maybe, sing me a song. Promise that you always will be there, hold my hand if ever I'm real scared. Help me stand up tall if I fall down. Make me laugh away all my bluest days. How could you promise you always would be there. Why'd you have to go away somewhere? Every morning and every night, do you watch over me like the sun in the sky? Am I all alone or standing in your light? I wish that I could, maybe... sing you a song tonight. ...You promised me we'd stay for the sunset...
** Listening to the song while watching the scene with Rika and her dad really drives the point home.
* Grani, especially his DyingMomentOfAwesome. A tireless, reliable "vehicle" program that acquired sentience, came to understand the threat of the D-Reaper and what was at stake, was repurposed as Gallantmon's "steed," and when too badly damaged to continue, told Takato and Guilmon that he cared about them and merged with Gallantmon to enable its Crimson Mode. He was like a digital version of ''Literature/TheGivingTree''...
** The entire final dialogue between Gallantmon and Grani is a combination of this, heartwarming, and awesome.
---> '''Grani:''' Do you want to fly? I will give you my wings.
---> '''Guilmon:''' Wings? I can fly?
---> (Grani appears)
---> '''Gallantmon:''' Grani!
---> '''Grani:''' I can no longer move on my own, but I can give you the strength remains within me. You can have my wings, Gallantmon.
---> '''Takato:''' Grani, you really are a Digimon, aren't you?
---> '''Guilmon:''' Grani, are you sure?
---> '''Grani:''' Yes, I am very sure, you are my friends, you talk to me. This is my gift to you.
---> '''Takato:''' GRANI!
---> '''Gallantmon:''' A PART OF YOU WILL ALWAYS BE WITH US, GRANI!
** Cue transformation to Crimson Mode and a Final Justice to the face for the D-Reaper!
* Dobermon's sacrifice to allow the main three to merge with their partners in the Real World and unleash their Megas. No matter if Alice is alive or a ghost she's heartbroken to lose her friend, and the tiny HopeSpot where the remains of his data become his head once more is shattered as the data completely vanishes.
** And then the following scenes as the news reports on the three Megas fighting the D-Reaper. All of their watching family and friends are ''terrified'' because they're watching their children fight a terrible menace but they're the only people who ''can'' fight it.