The fight with Tai and Matt over the former's reluctance to use Omegamon.
Episode 2: Pure Sincerity
Joe and Mimi's talk about their issues.
Not to mention the effect it has on Gomamon.
Gomamon: Joe? Do you not want to be super fish buddies anymore?
Episode 3: Back to the Beginning
Patamon telling TK to kill him if he goes berserk from the virus is just as emotional here as it was in the original.
TK in general is this in episode 3, as his need to engage in weird habits that are different everyday are revealed to be a coping mechanism over the constant losses he suffers.
The fact that he's trying to stay in-character when an infected Patamon starts biting at him. You can easily see his facade slowly breaking.
Izzy revealing that he doesn't feel like he has anything if he loses Tentomon.
When Hackmon asks that wasn't it Daigo who led the original DigiDestined against the Dark Masters; Daigo has a flashback to what seems like his partner LoaderLiomon's final stand against Piedmon ending with the Dark Master seemingly killing LoaderLiomon.
Meicoomon attacking Meiko, ranting on and on about how stressful a time she's had until Meiko calms her down.
Tai and Matt being completely resigned to drowning in MetalSeadramon's lake. How accepting they are of an impending death really drives home how accustomed they are to mortal danger.
