This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Taiyou Sentai Sun Vulcan
Episode 11. A scientist's young daughter dies of an illness, which is sad enough, but then Black Magma builds an android copy of her to get him to make them a deadly poison. It spends the episode alternating between being cute and creepy-evil, but in the end when the Zero Girls order it to kill the scientist, its loyalty to the real girl's father trumped its loyalty to the villains. This guy basically had to lose his daughter twice. After that, the beatdown that the Monster of the Week received was welcomed indeed.
Meta example: 11 months after the show ended, Shin Kishida, who played Daizaburō Arashiyama, died of esophageal cancer. VulPanther's actor, Asao Kobayashi, was so overcome with grief at this sudden death that he took a hiatus from acting and retired from show business entirely not long after.