Gohan: Think, what would my dad do? Goku:[in Gohan's mind] Bye, son! Gohan: I'm beginning to think I have issues.
Freeza's beat-down of Vegeta.
Freeza: You see? It's just like I told you. Like a bitch.note Freeza told Vegeta earlier that he would be "crying like a little bitch" by the end of their fight.
And after Freeza kills him.
This conversation just before Goku arrives and Freeza kills Vegeta out of spite.
Freeza: It seems our game is over, Vegeta. Now that we're done here, it's time to send you crying home to mommy. Vegeta:My mother's dead. Freeza:I know. note Cui had made a similar statement, but Freeza's has more gravity since he definitely killed Vegeta's mom along with the rest of the Saiyans on Planet Vegeta
Goku's reaction to Vegeta's death:
Goku: C'mon, you deserve a proper burial. Freeza: Ah, yes. A proper burial: an unmarked grave on an empty planet in the middle of Nowhere, Space. Honestly, I'd say it's too good for him. Goku: I'll be sure to give Freezer one for you, best buddy. Goodbye.
Just like in the source material, the Bad Future Trunks comes from. Especially Yamcha's fate. This fate is the above picture.
Goku's reaction to Freeza killing Krillin. You can hear from the sound of his voice that Goku was trying to hold in his tears.
Tien's reaction to Chaotzu's death. Great bit of acting from Ganxingba.
Vegeta's treatment of Trunks in Episode 38 is quite sad to watch note Which will make Vegeta's fight with 18 much more satisfying to watch.:
Vegeta: I'm sorry but...I don't listen to bastards.
Trunks: Oh come on, we both know I'm your son. Vegeta: And are you as disappointed as I am? Trunks: *growls*
Even later, when Vegeta sees "the real Androids" that Trunks warned them about...
Vegeta: Wow, you're just the Grand Central Station of disappointment, aren't you? Trunks: <upset> How are these people friends with you!?
Immediately lampshaded by Tien who essentially tells Trunks that they aren't "friends" in any sense of the word. They pretty much just embody the whole enemy of my enemy is my friend idea, which in no way states that they have to like each other. The Z Warriors and Vegeta are like Vitriolic Best Buds minus the best buds bit.
Vegeta's abuse towards Future Trunks does not lighten up either, as the moment Future Trunks tells Vegeta that he's not as strong as Goku to his face, Vegeta snaps and winds his own son.
On another note, it's just sad that Trunks knows absolutely nothing about the man. His reaction to when Piccolo told him that Vegeta once tried to kill everyone is nothing short of horror and shock. It's possibly (and sadly) justified in that Vegeta has done nothing that would make one even want to tell his child(ren) about him. Hell, the best thing that the mother of his child could say about Vegita to a young Trunks was "You share his gender." Ouch.
Yamcha looking on while Goku is screaming in pain as he suffers from his bacon-induced heart attack, while the spoken dialogue is Played for Laughs you can tell he's real worried about him, probably the only one of the gang that Yamcha can consider a friend.
The thought of having to just stand there watching your friend suffer due to an extremely painful condition, knowing full well there's not a damned thing you can do about it can evoke tears...
On a similar note, the two instances when a giant enemy is torturing a helpless Goku, first Ozaru!Vegeta, then Giant!Lord Slug, by squeezing him so hard it makes his lungs squeak like a dog toy. It's played for laughs, but Goku's pained screams aren't, and you can tell he's hurting horribly.
And now TFS has a Do you Want to Build a Snowman parody, only replace "we're orphans now and only have each other" with "we're an endangered species and homeless now and only have each other". And a few years after Nappa says this, Raditz dies and Vegeta murders him.
There's also the fact that Nappa doesn't remember Raditz's name during the song. Raditz actually was stronger than Goku at that point, but Nappa only remembered the latter's name.
Kami's revelation about why he's putting off assimilating with Piccolo, bringing up a lot of Fridge Horror about Kami's existence in the process:
Piccolo: But if you don't fuse with me, the entire world you're guarding might be destroyed! Kami: Maybe I'd rather it be destroyed, then ever have to be part of you again! ... Kami: Listen, Piccolo. I've been the guardian for over three hundred years. I've seen wars, sickness, death, and far worse. All the while trapped on this lookout. Unable to interact with the outside world for more than moments at a time. Now the only chance I have left is to give up my free will to someone else. It's just another prison. Piccolo: ...Wow I... I didn't- Kami: It's fine. I'm done anyway. You're right: If I don't do this now, we are likely to lose everything.
"Mom? Dad? Please stop fighting."
The music during Kami's monologue really drives home the melancholy, too. All in all it is a surprisingly heartfelt scene.