This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Duck Dodgers
During Duck Dodger's confrontation with the Martian Queen in "The Queen is Wild", Dodger's informs her that he's "never had any complaints from the ladies" when she questions his skill with the laser nunchucks he sports. You can hear the hurt in her voice as she says, "The ladies?"
Of course, this whole thing started with a broken engagement between Dodgers and The Queen. Tricked by Commander X-2 into thinking that the sole purpose of the King was to oversee the Methane Farms of Uranus, Dodgers immediately believes the worst of the situation, and without bothering to confirm this with the Queen, declares the engagement off, telling her that his affection for her was all part of a Matahari-style ruse to gain her confidence and learn Mars' secrets, then leaving her alone in her bedchamber on the eve of what was to be their wedding.
In "Duck Departure", an understandably frustrated Dodgers informs allies and enemies alike in the middle of a confrontation that he's had enough and quits, that he's going to ply his skills elsewhere. The response of his archenemies, his colleagues, and the Martian Queen, who had just called to inform Dodgers that she was taking him back, is an incredulous "Skills?!" and gales of laughter. Think about it, even the one woman who actually sees him as a romantic interest doesn't think he's all that capable.
The second-to-last scene in "The Fowl Friend." Doesn't really help that it's a word-for-word Shout-Out to the Giant'sHeroic Sacrifice. After Roboto flies into the meteor and destroys it and himself, the scene turns into Mood Whiplash when Dodgers says, "I sure hope that table holds."
Commander X-2 being dumped by the Martian Queen at their wedding in the season three premiere when Tyr'ahnee decides that her heart still belongs to Dodgers. It's especially heartbreaking because the Martian Queen's response to Duck Dodgers continuing to reject her affections is to revoke the peace treaty Mars made with Earth at the end of season two.