One MC thinks the other is dead - biggest gut punch descriptions

Even if it is for a short time, what are the most heartbreaking instances of one MC believing the other is gone for ever? I read two examples in which I genuinely felt (for a few moments) that the author might actually kill off an MC for the shocking moments (and then remembered I was reading a romance book so that should ideally not happen).

{The Work of Art by Mimi Matthews} - >!the MMC has been paranoid about his wife's initial intended planning revenge on her and tightened the security and restrictions for her at their new home. The FMC gets badly hurt and he finds her bleeding and without a pulse with her loyal dog beside her, leading to an agonised cry of heartbreak from the stoic MMC. The last thing he'd said to her had been sullen and angry so that is double the pain.!<

{A Heart Sufficient by Nichole Van} - >!the MCs' dinghy capsizes and they are thrown into the water. The MMC desperately dives into the water repeatedly to find his wife to no avail and starts breaking out into sobs as the minutes go by. Their marriage up till now (and even their relationship before) had been very strained and even hostile. The MMC almost drowns because he gives up once he believes he's lost her and bitterly regrets his behaviour towards her, hoping they can meet in the next life on happier terms!<

There does not have to be the regret about the parting words but I think that usually accompanies.