This is based on opinion. Please don't list it on a work's trope example list.
Tearjerker / Strike Witches
In the ending of second episode of first season, when Yoshika, with Mio, visits the grave of her father. When Mio reads the message in the grave: “use this power to protect people”, Yoshika finally understands why her father abandoned her. It was for save people's life. She starts to cry in his grave.
Genki Girl Lucchini breaking down in tears during episode 11 of Strike Witches 2 when it's discussed that if the coming offensive fails, they'll have to abandon her native Romagna to the Neuroi.
When Mio Sakamoto has a breakdown in Strike Witches 2. "Let me be one of the chosen" she says crying into Minna's arms.
Pretty much all of Minna's flashbacks in episode 8 of Strike Witches. Her boyfriend Kurt volunteers in the military so he can be with her. Minna makes it out of Gallia during the evacuation, but he does not, and silently apologizes for failing his promise to see her again seconds before he's killed by the Neuroi.
Also, the SW-verse Operation Dynamo compared to the real thing. Instead of being a six-figure evacuation of Allied forces from a northern province, it's a complete evacuation of Gallia, a sure logistical nightmare for a country of 40 million people. The current ruined state of Pas de Calais and Kurt's demise do not paint a pretty picture of what happened.
Barkhorn's lament about being unable to save her sister from Karlsland's destruction in episode 4 of Strike Witches. As such, she decides to go out in style fighting the Neuroi, especially after first meeting Yoshika.