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Tear Jerker: Call Of Duty Black Ops 2
Farid executing Harper to maintain his cover as a CIA agent. Made worse by Harper screaming at him to "do his job" while Farid holds a gun to his head, and then even more so when - even when Section arrives seconds too late and tells Farid that it's okay, that he did what he had to do - the camera shows Farid broken and in a state of shock at having killed Harper.
Farid is screwed either way. He can kill one of his best friends, or he can try to shoot Menendez. In the latter option, Menendez dodges the gun, shoots farid in the stomach, rants for a bit, and then executes him. Poor guy...
Farid dies in most of the endings, either by failing to kill Menendez, or trying to stop Salazar from shooting Karma/Chloe.
When Woods is ordered to shoot an assassination target, only to find out he was tricked into shooting Alex Mason. Then we see young David Mason's reaction when he sees his father lying in a pool of his own blood, presumably dead.
Also Hudson sacrificing himself to save David and Woods.
Menendez failing to rescue his sister, and then seeing the grenade explode in her room.
Everything about Josefina counts, if only to remind you that Raul Menendez loved his sister more than anything in the world. The masks on the wall always stand out, as if he wanted to protect her from her ugliness. And the terrified, desperate wailing she makes when she's dragged out of bed? Borders on Nightmare Fuel...
Wood's death if Karma is dead and Menendez is spared. Menendez infiltrates the Vault, kills Woods with Josefina's locket, and lays him down gently on his bed. Very slightly dulled, considering Woods is currently 95, and doesn't seem too phased by Menendez appearing in his room.
Salazar's betrayal and subsequent death, if Harper is alive. The guy's been with you in all of the 2025 missions, and is actually a decently coded teammate that helps you push forward on his own if left alone. And he turns out to be in league with Menendez, and through his actions, allows the US Army's drones loose on China and America, causing countless deaths.
Mendendez's suicide in the "worst" ending is a twisted example. After escaping from prison and killing Woods, he goes to his sister's grave, digs her up, smashes open her coffin and calmly pours gasoline over himself. Then, while looking at her remains... he lights a match. It's a poignant yet chilling way to depict a character that was so utterly consumed with vengeance that once he achieved it, he had nothing else to live for. So he decides to end his own life, and be with his sister.
In the same token that it's a heartwarming moment, Mason having to tell his son he's duty-bound to save Woods is a sad moment as well. Alex really doesn't want to break the promise he made to his son that he put his military life behind him and David is also disgusted that his father is going back on his word. It's not a comfortable moment for either party.