This is heavily implied to be why Tiger became a superhero and Spinnerette's mentor. His wife demanded he give up crime-fighting out of fear of him dying. He complies... until a gunman opens fire at his daughters' school. His daughters were fine, but the news traveled slowly.
The Korean webtoonTrace is unique among other X-man-esque spin-offs in the fact that it follows the journey of a middle aged business man as he develops mutant powers, rather than the usual gang of high school teenagers. Since this a Crapsack World he lives in, his wife and daughter are taken away by the government under the pretense of normal screening and testing, when really they are used for human experimentation. The protagonist doesn't realize this until he breaks into the facility, where he is greeted by the sight of his wife's head floating in a vat. Talk about preying on a typical father's worst feelings of helplessness.
In the "Just Today" story arc of Something Positive, Davan's father Fred has to deal with being diagnosed with Alzheimer's. He asks his wife Faye to take the day off from work to spend time with him so he can tell her. In the end, he can't bring himself to tell her and they just spend a peaceful day together. As they go to bed for the night, she thanks him for spending the day with her and they share a goodnight kiss (the caption for this strip is "Sometimes it's about life...". The next morning, Fred realizes that Faye died in her sleep (the caption here: "Sometimes, it's about fear").
Homestuck: Poor Jane's dad. It's hard enough that there have been attempts on his teenage daughter's life, but then he had to watch her get blown up by a letter bomb...
More generally, a major theme in the webcomic is kids inheriting, and being screwed up/over by, the mistakes of those that came before them. A fear that many parents have.
The "bishounen virus" storyline of Manly Guys Doing Manly Things has Commander Badass getting rejected by his children because the virus has rendered him unrecognizable and scary to them. Word of God is that this was based on an incident when she was a little kid and her dad shaved off his beard; a lot of readers turned out to have similar stories.
In Yosh!, Kate's father explain that he searched her for months, following any lead he could find, including obituaries.
Fans!: Alysin's parents dealt with the helplessness of watching as their daughter suffered from a rare and deadly disease, to say nothing of the severe personality changes that resulted. Will's father murdered his mother, and Will lived in fear that he would turn out like his dad. Shanna reined in her imaginative impulses, fearing that she would end up like her insane mother.
Jae Gu of Girls Of The Wild has been raising his younger siblings for years, after the death of their father and abandonment of their mother. He absolutely freak out when they get food poisoning from spoiled sushi, carries them to the hospital barefoot, crying the entire way. By the time he makes it to the hospital, his feet are so cut up he is leaving large bloody footprints wherever he goes and still is more concerned with his siblings then getting his feet bandaged.
In Unlife there are several, most of them about children - such as your child gone missing during a catastrophe, a zombie outbreak at that. In one heartbreaking background story a mother turns in to a feral zombie and devours her own children.