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Tear Jerker: Tekkaman Blade
Barnard O'Toole's first appearance, where he shared his whiskey to his fallen teammates and taught D-Boy the meaning of wars: that survival is all that matters because it means that you can protect your comrades in the future.
And just a few episodes after the above event, O'Toole's lover, Angela, Heroic Sacrifice in order to save D-Boy and telling him that she's also in his memories now as well as telling him to never forget about his hatred for the Radam. This is topped with Angela saying that she'll be with O'Toole soon enough before firing the shot that saves D-Boy's life.
As much as Shinya/Evil's last moments just seems to satisfy his sense of jealousy, you've got to feel rather teary when Blade, in anguish, STOMPS the Radam bug that controlled Shinya, too late to learn that if he could find that earlier, he wouldn't need to kill Shinya/Evil. This is continued with how Blade prepares his last assault against Omega, declaring that D-Boy or Takaya Aiba is dead, only Tekkaman Blade remains... continued with Aki's ignored pleas for him to stop... even with her crying.
Takaya's/D-Boy's entire life in general. The poor guy never got a break. Let's recap, shall we?
First, his family and friends were forcibly converted into Tekkamen by the Radam. The "beginning of the nightmare" according to Takaya's story in Episode 24.
Second, his dad sacrifices himself as well as giving Takaya the task of killing his own siblings just to stop the Radam.
Third, having to watch his youngest sibling, Miyuki, one of the few incomplete Tekkamen who couldn't be taken over by the Radam, sacrifice herself in order to save the Space Knights' lives, despite his best efforts of trying to save her.
Fourth, having to fight against his old mentor, Goddard, now known as Tekkaman Axe in order to reach the Moon and throughout the fight, you get snippets of how well Takaya and Goddard got along with each other.
Fifth, losing some of his newer comrades like O'Toole and Angela.
Sixth, slowly losing his memories because of his Blaster Mode upgrade.
Seventh, being forced to kill his younger twin brother, Shinya, now known as Tekkaman Evil, and his older brother, Kengo (Tekkaman Omega), at the end of the series in order to stop the Radam. His grief after killing Shinya and the scene before his Final Voltekka against Omega seals it.
Finally, after all of that, after saving the Earth from the Radam by having to kill most of his old friends and his own siblings, he loses his memories. All of them. However, this frees him of the burden of his past and is able to give him a new life with Aki.
The episode where Takaya goes back to his old house with Aki. The flashbacks of how his life was before the Radam completely destroyed it will make you teary-eyed.
The scene with Takaya opening the time capsule that he and Shinya buried approximately 10 years before the show started. Listening to Shinya's recording finally makes Takaya shed tears and cry in anguish.
Balzak's death. Balzak sacrifices himself in order to save the Blue Earth from Sword's attacks with his last thoughts being for Lille, his pregnant girlfriend/wife-to-be, to take care of herself before he burns up on re-entry. The worst part is that Lille somehow senses this.
Beforehand, Balzak leaving his life with Lille and Rick behind in order to help the Space Knights against the Radam. Lille says to herself that she and the baby she's carrying will be waiting for him to return. Sadly, this won't be the case and Balzak will never get to meet the child that he conceived with her.