This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / The Protomen
Don't turn your back on the City.
This trope is why the Protomen don't often play "The Stand (Man or Machine)" and "The State Vs. Thomas Light" in live shows—the songs tearjerk the band.
If it involves Dr. Light, it's either sad by default or will end up sad.
"Beard's Going Nowhere" is mostly fun. Then you get to the parts involving Emily and it becomes a mixture of funny, heartwarming, and heartbreaking, especially in light of Act II.
When I was younger, things were different And a man was allowed to be a man But I grew up too fast, like I was racing with the devil I've felt the blade so many times Emily, girl, won't you take my hand and we'll ride Across the barren face of this desert road You set my wheels on fire I'll rev my engine till the sound is just deafening Emily, girl, I swear we'll make it out of this wasteland...
Live shows have the potential to make sad songs even sadder, particularly "The Stand" and "The Sons of Fate." Sometimes you can see/hear Panther crying.
The Protomen's Queen cover CD insert is both an homage to the Queen II CD and a representation of both Acts. What makes it a Tear Jerker is what's featured there. You have Megaman and Protoman's helmets, Joe's dead body, Emily in the skies, Light straining to stop the gears while Wily casually moves them forward, and the kicker is a noose around Light's neck, held by the image of Emily.
Some of the songs covered can be heartwrenching, such as "Somebody to Love."
In one of the Cover Up's story tracks, Light is asked about Emily and says she was a fighter. In an earlier track, he had this to say to Emily's spirit.
"I need you to know something... the way we used to be together... it was real. And no matter what happens tonight... no one can take that away from me. Or us. I gotta go now. I’ll see you soon."
The Cover Up album is the soundtrack to a movie made during the time skip in "How the World Fell Under Darkness." It fills in some of the blanks about the time between Light’s exile and "Breaking Out." Apparently, Light is on the run from Wily and receives help from a reporter who is one of Wily's moles.
Protoman's death in "Hope Rides Alone" .
"Funeral For A Son." The entire song, especially in light of Act II. In particular, from the liner notes:
Light notices a tear streaming down the dorsum of his hand and feels a breathtaking weight in his chest. What is this? Frustration? Humiliation? Hatred? Certainly, these are there too.
But no, this is more than that. These emotions are his life. He has lived with them for so long that they no longer affect him. Over the years he has learned to fight them, then to ignore them, and finally channel them into his work, his creation, his machine, his son.
While "Unrest in the House of Light" is sad in and of itself, the demo version has more of an emphasis on vocals, and is more dramatic.
Light's lines in "The Will of One" echo Emily's last words, as revealed in Father of Death.
Protoman's entire tone in "The Stand." Made worse when he's proven right.
You can actually hear the Machine Monotone of his voice falter while he's speaking at some points. "They'll watch you die to save their lives! They will not stand here by your side..." He was genuinely heartbroken that no one in the crowd tried to help him, or at the very least continue his fight.
"The Sons of Fate", as Megaman is forced to fight and kill his own brother by the people he's trying to save.
The two brothers stood feet apart. Both in pain. Only Protoman fell. His knees hit the ground. His weapon followed. Before he could fall any further Megaman was at his side. The brothers, the Sons of Light, embraced. Protoman was dying. Nothing could stop that now. Protoman looked up through strained eyes and tried to speak. At first nothing came. Summoning all his remaining strength, Protoman whispered into his brother's ear...
And after his speech and death, the crowd rubs salt in the wound:
The crowd, to Megaman: Why do you cry for him?
This one line, where it is truly driven in that Protoman was right:
Megaman: We both know they'll never fight!
Live shows can make it even more heartbreaking; even if the banter before is silly, the song itself is played straight.
Megaman screaming the line "You are not evil!" at Protoman.
Protoman's last words in "The Sons of Fate." They echo Light's words in "Unrest" and "The Will of One."
Protoman: If these people... tell this story... to their children... as they sleep... then maybe someday... they'll see that a hero... is just a man... who knows he's free...
When Megaman finishes reciting his original creed with new context, the line after it sounds almost as if he damaged his vocal processors by expressing his grief.
When Megaman turns his back on the people because they don't understand what it means to stand up for themselves, and tells them that they're the dead, it hurts. The liner notes make it worse, pointing out that Wily's robots are completely indiscriminate in their slaughter, killing everyone, man, woman, child, without any hesitation. As the wail of "We are the dead" slowly fades to the windblown streets, it's heartwrenching.
"The Intermission" has the contents of Tom's letter, especially the end:
"In the meantime, please be careful. This world is getting darker all the time. I weep at the thought of something terrible happening to you. I could not bear it. All my love, Tom."
These lines from "The Good Doctor," as the violins kick in and Light's voice catches on the last part:
Light: The one I love, she works so hard... works her fingers til they bleed... Some of the pain that she endures would bring a strong man to his knees. And I only want to help...
Emily's last words.
Emily: No matter how dark this City gets, there will be—
When the reporters ask Wily the name of the girl who was murdered, he callously states that it doesn't matter.
The entirety of "The State Vs. Thomas Light." The song itself is sad, and Light seems driven to tears at several points.
Joe's speech to the girl in the bar in "Breaking Out," given what eventually happens to him.
So kiss me fast cause there's no time to lose/Leave the light on, I'll come back for you/When everything is said and done, I swear I'm gonna make it right...
The prototype lyrics, too.
So kiss me fast cause there's no time to lose/I promise someday I'll come back for you/And if I die, don't blame yourself; we all do what we think is right...
"Light Up the Night" has this line:
Light, in reference to Wily: "Well, a friend once told me, men, they would follow any man who would turn the wheels..."
Joe's death in "The Fall," combined with the triumphant chorus dying down.
It took at least one person over half a year after the first listen before he didn't have to avoid the song because of how badly it affected him.
This bit from the liner notes:
He thought of the children. How, for the first time, they would know a world without that screen. Without the constant, mind-numbing barrage of misinformation. Silence. Had he ever encountered silence? Soon.
"Here Comes the Arm" has the contents of Emily's letter.
Light: This is not the world my father knew... This is not the world I know... he would've wanted me to build...
Light's request to Joe. "When you see Emily, tell her to wait for me, 'cause I still have work to do."