This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / On Her Majesty's Secret Service
Bond's reaction at his wife Tracy's death. "We have all the time in the world..."
The original draft had them drive happily off into the sunset and then have her die in the pretitles of the next film. The way it turned out makes it even more stark.
It's even worse if you pay attention in later films, and realize she's the (Watsonian) reason there's a different Bond girl every film: he can't get over her. (The Doylist explanation, of course, being the financial practicalities of having non-recurring Bond Girls.)
What makes it even worse somehow is the way the soundtrack switches from a sad reprise of "We Have All the Time in the World" to this off-kilter, borderline manic version of the James Bond theme, and it just sounds really, really off. All while focused on the lone bullet hole in the windshield...
To make the impact all the more shocking, the entire scene up until the final seconds takes place without any music. As the gun goes off and Bond suddenly sees that his new wife isn't speaking, it's completely silent. Nothing but Bond and his wife...
Perhaps the worst part is the very end when we hear Bond start to cry offscreen right before the credits roll.
Even knowing it's going to happen doesn't lessen the impact when it does. Seeing James Bond, the secret agent and Royal Navy officer who will never give up, go into flat out denial about her death... that really hits to a fan.
Tracy's backstory (teenage rebellion, infidelity, dead child, dead husband).
Somehow, Bond's wedding manages to be this regarding Miss Moneypenny and Q. Moneypenny crying at Bond's wedding is one of the saddest things of all time, and it follows the only time that Q calls Bond by his name instead of the usual "007" ever in the series.
Try reading You Only Live Twice after you've finished this one. Even though 8 months have passed, Bond's still broken by Tracy's death and can barely keep his job, stumbling around London in a drunken haze, blowing assignments, gambling his pay away and looking forward to his next hangover. And even as he goes back to normal, it's very clear that he will never get over his greatest loss.
The ending has a traumatised Bond quietly cradling the bullet-ridden body of his dead wife, muttering "We have all the time in the world" repeatedly.