Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Tear Jerker: Kinnikuman
"A...man such as me didn't kn...know these feelings of Kid...forgive me, ki...Kid..."
—- Kinnikuman Zebra.
"I wanted to be a Choujin, so I could serve the world and its people...but no matter how hard I tried, I was still only human...but my heroes kept pushing on, and somehow I understood when I defeated Sunshine...Even if you're just a human, you can be even greater than a Choujin, as long as you have the immortal soul of one..."
—- The last words of Geronimo, the greatest human ever to live in this series.
We know what you're thinking and before you say anything, no, this isn't a mistake. An action-comedy manga like Kinnikumancan have really sad moments.
Seven Devil Choujin Arc
While Wolfman/Rikishiman's death in the Seven Devil Choujin arc might have been somewhat Narmful, Kinnikuman's reaction to it...is actually quite sad. Remember, this isn't Kenshiro who's prone to Manly Tears, this is Kinnikuman, who is always the guy either cracking jokes or being the butt of a joke (even when it's serious), breaking down in tears and going berserk while saying "It's All My Fault!".
Unlike the example above, in that same arc, Robin Mask's death was actually a Tear Jerker, made worse by the fact that his wife, who was searching for him since he had run off without her had finally found him only to see him die in front of her.
Alisa: I finally found you...and our reunion is like this...
The Seven Devil Choujin arc continues to get worse for the Justice Choujin, as another one of their members dies; this time it's Warsman, who was once evil. What's worse is that it's in the way that Warsman died; Warsman managed to harness the power of Kinnikuman's Burning Inner Strength from their fight, but it doesn't really help him because Warsman is prone to malfunctioning if he goes past his limit, meaning that using against Buffaloman would be akin to suicide. He uses it anyways, but misses and lands right into the horns of a charging Buffaloman.
What's even more heartwrenching is Kinnikuman's reaction to Meat-Kun's presumed death. After he assumes that he was too late to save him, he breaks down in tears. It may not be the half of a Tear Jerker as his prior reaction to Wolfman/Rikishiman's death but it was depressing enough to make Kinkotsuman, Iwao, Akaiwa/Gobugari, Yosaku and the whole crowd cry in their seats. Fortunately,Meat-Kun wasn't quite dead
When Geronimo, who had saved the lives of Kinnikuman and co. twice, is about to die from critical injuries he sustained in his fight against Sunshine, the Justice Choujin decide that the least they can do is give him some of their Choujin Power so he can recover. His body rejects it, the reason why it failed being more than clear to all of them even before Geronimo himself admits it: he's actually a human, meaning that it was pointless of them to do that.
Geronimo's last words make it even more of a Tear Jerker.
Choujin Dream Tag Team Arc
Prince Kamehame's death.
Even the Devil Choujin have their sad and heartwarming moments, shown when Sunshine stops his "Cursed Roller" technique before Kinnikuman Great goes through it: because Ashuraman's arms were stuck between the rollers, stating that "Devils have friendship too!". Ashuraman calls him an idiot...only for it to be revealed that Ashuraman's in tears because of this kind act. It doesn't just stop there, Ashuraman, still in tears, still asks Sunshine why he would save like him, someone who was raised to be evil. Sunshine says something so tearfully heartwarming that even the crowd that were viciously booing the both of them is moved to tears.
Sunshine:It doesn't matter if we're devils! I can't abandon the person who's fighting this battle beside me to the very end!
We then get to see a flashback to the day where Ashuraman's teacher, Samson Teacher, sacrificed his life to save his pupil.
The loyalty between Kinnikuman Zebra and pet zebra, Zebra Kid, already mentioned on the Heartwarming page. The flashback of them being together is already sad because it ended with Zebra having to kill Zebra Kid in order to enter the Choujin society.In the match between Kinnikuman and Zebra, however, it's turns the sadness Up to Eleven we get to see The spirit of none other than Zebra Kid possess Kinnikuman when he's trapped in the Muscle Inferno, in order to show Kinnikuman his side of the story on the day he was killed; he could have easily escaped the Muscle Inferno, but was so loyal to Zebra that he didn't move and faced his death just so Zebra could get into the society. Kinnikuman divulges this information to Zebra after defeating him, which causes Zebra to cry tears of blood. There's a reason why Zebra's last words are quoted at the top of the page.