This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / El Chavo del ocho
The episode where El Chavo is Mis-blamed for theft, ostracized by everyone and leaves temporarily. It traumatised several generations: seeing everyone calling him a thief at his face is pretty hard to watch, and the scene that follows with El Chavo leaving the vecindad is even more heartbreaking, specially the part where he looks at his iconic barrel and touches it one last time before leaving. Made even better or worse by the ending: when El Chavo is cleared, he is talking to his friends about the time he spent away from the vecindad: he had gone to a church and, after being counseled by a priest, he decided to pray to God. Chilindrina and Quico assume he was praying for the thief to be caught, but Chavo instantly corrects them, saying he prayed for the culprit's reformation. The thief, Sr. Hurtado overhears this and is so touched that he has a Heel–Face Turn and not only returns everything he stole, but he also gets El Chavo a ham sandwich.
Another one is when Profesor Jirafales tells Don Ramon that he (Profesor Jirafales) truly loves teaching and genuinely wants the best for his obtuse pupils. The kids overhear this and they write on the blackboard: "We all love you sir!".
A double episode begins with El Chavo sleeping against Don Ramon's door because he had been promised to have breakfast and the kid didn't want to "let him run away with it" (it works, believe it). The two parts that compose this episode, despite hilarious, are filled with small moments of pure Tear Jerker.
El Chavo: (waiting for Chilindrina to bring the eggs for breakfast) Why is she taking so long...?
Don Ramón: Calm down. Can't you hold back hunger for five minutes?
El Chavo: (soul-crushingly slow) I've been holding it back for eight years...
Sr. Barriga: (after the breakfast eggs got broken and ruined) You mean that those eggs were for Chavo's breakfast?
Don Ramón: And mine too. For the whole week.
To make things even worse, the two-part episode ends up with El Chavo never getting his breakfast, and sleeping again against Don Ramón's door, hoping that, next morning, he may have a new chance. Cue sad background music, credits roll, and a box of napkins...
In the Animated Adaptation of the same episode, they added a last extra scene to give it a heartwarming ending: Quico leaves for a moment and then returns with a ham sandwich for El Chavo.
A great example comes from the episode right before the Beach Episode. By a series of events, every inhabitant of the Vecindad leaves to Acapulco. By the end of the episode, El Chavo is the only one around and we are greeted by some sad background music. Cue Sr. Barriga's arrival and, when he's told everyone is gone to Acapulco, he decides to go as well. He leaves, and when he's nearly gone, he stops, turns, and looks at El Chavo, alone in an empty Vecindad. Mr.Barriga tells him "Hey, Chavo... Want to go to Acapulco with me?", followed by Chavo's stuttering, hesitanty, soul-crushing reply: "M...Me...?"
Another one comes from a Christmas Episode. Señor Barriga gave all the boys a little toy truck as a present. Later, near the end of the episode, El Chavo tells Quico about the neighborhood's doorkeeper's child, who has no toys, and then leaves with the truck, without warning. He then returns shortly afterwards while Don Ramón and Quico were looking for him, and wondering what he was doing.
El Chavo: (Without the truck) They are going to think Santa Claus gave it to him.
Don Ramón: What?
El Chavo: Why, the truck! Didn't you see that I threw it through the slit of an open window?
Quico: (Surprised) You gave your toy truck to the doorkeeper's kid?
El Chavo: Well, of course! Didn't you see he's a poor child? (Cue Don Ramón and Quico looking at the camera, speechless)
In the episode where the characters are looking at old photographs, we have the last conversation Doña Florinda had with her husband. It is played rather comedically, with him talking using Quico's maneirisms, like "¡Cállate, cállate que me desesperas!", which he says before he leaves to die in his job. Then, you realize that the last freaking thing he said to his wife was shouting at her to shut up. You feel like a jackass for laughing at this scene right after that.
It doesn't help that right away she tells baby Quico that she has the feeling they're not gonna see him ever again. As if understanding, Quico leans against his craddle to cry the way he always does.
If we go to the tie-in books, we have El Chavo describing how nobody wanted to adopt him in the Orphanage of Fear, and by the end how El Chavo finds Jaimito the mailman dead in his apartment, having passed away of old age. He at first can barely understand what happened, believing that he's just sleeping; then he realizes the truth and naively thinks "Well, Mr. Jaimito always said he was tired... now he can sleep and no one will disturb him, ever."
Thankfully the animated adaptation ignores that event and Jaimito is alive and well, still finding ways to avoid work
It does become a Heartwarming Moment when Chavo and Chilidrina end up seeing each other again after everyone one leaves and chuckle at the insanity of the situation before running into each other's arms, with Chilidrina in tears of happiness.
One can get a bit teary-eyed when learning how the relationships between Chespirito and his cast members became, especially with Carlos Villagrán due to rights over the characters. It does become less tearjerking after reading up that they all ended up on good terms.
The real life death of Ramon Valdez in 1988, who played Don Ramon (who was arguably the most popular character in the show, although he had left in 1981). Most fans agree that the show was never the same without him.
The same could be said for the passings of Angelines Fernández (Doña Clotilde "la Bruja del 71"), and Raúl 'Chato' Padilla (Jaimito the cartero), both in 1994, Horacio Gómez Bolaños (Chespirito's brother, who played Godinez), in 1999, and Rubén Aguirre (who played Profesor Jirafales), in 2016.
Of course, the death of Chespirito himself in 2014 may be the ultimate tearjerker, and probably makes all of the series' sad moments worse.
At Quico's birthday, El Chavo steals some sandwiches and puts them into a bag. Later, Quico wishes for no one to come to his next birthday to have all the cake for himself, but Doña Florinda tells him he should wish for the opposite, for them to learn how to share. When Quico wonders whether learning to share is difficult, the following scene shows El Chavo giving half the sandwiches to Don Ramón, who in return gives El Chavo a drink. Despite his poverty, El Chavo was perfectly capable of sharing whatever he had with those in need.
Also qualifying In-Universe, every time El Chavo reminds people of his poverty or that he hardly ever eats.
In a episode from the last seasons, Doña Clotilde buys lollipops for the children, but Ñoño surprisingly come to the vencidad, leaving El Chavo without one. He tries to hide, but he clearly wanted one. In the next scene, Doña Clotilde arrives in the vencidad and quickly gives two lolipops to El Chavo, compensating for what happened early. Then Ñoño arrives again in the vencidad with a guilty face. El Chavo takes a look at him and asks if he wants a lollipop, then Ñoño, revealing a lollipop he was keeping in his clothes, says the same, offering his lollipop too. Both start to smile and they give a big and long hug. This becomes a huge tearjerk moment when starts to play a heartwarming soundtrack and Ñoño starts to cry for real.