Harsher in Hindsight

Leland: 1993. World Trade Center bombing, remember? During the trial, one of the bombers claimed the CIA had advanced knowledge. The diplomat who issued the terrorists' visas was CIA. It's not unthinkable that they paved the way for the bombing, purely to justify a budget increase.
Mitch: You're telling me that you're going to fake some terrorist thing, just to scare some money out of Congress?
Leland: Well, unfortunately, Mr. Hennessey, I have no idea how to fake killing four thousand people, so we're just going to have to do it for real. Blame it on the Muslims, naturally. Then I get my funding.

—The Long Kiss Goodnight

Harsher in Hindsight is a serious event or plotline where a later event (in the story or Real Life) comes up and only serves to amplify the effects of the already bitter-tasting effect. It can lead to episodes or issues being pulled or held from re-running if it's perceived as Too Soon.

This leads to a rather heart-wrenching moment and makes some people feel uneasy about it when they view the event in the original work.

Compare Funny Aneurysm Moment, Too Soon, and Cerebus Retcon (where elements that were originally comedic are later deconstructed and played as tragic).

Note that if the event in question is something inevitable, such as people dying, that's not necessarily this trope. Everyone dies eventually, as far as we know. It would be this trope if the death had some link to how they appeared on screen.

Contrast Hilarious in Hindsight, Heartwarming in Hindsight.

WARNING! There are unmarked Spoilers ahead. Beware.

Examples of Harsher in Hindsight are listed on these subpages: