It's been over 24 hours so:
In what episodes has the Enterprise D's warp Core threatening to, threatened with, or actually did explode?
I might have missed some, but here goes
All good things...
Parallels (If you count the Enterprise that blew up)
Cause & Effect
& of course the Generations movie
Close, but not quiet.
Maybe rephrasing the question will help:
In what episodes has the Enterprise D's warp Core been threatening to, or actually did explode; and was threatened to such extent, that it would explode?
I am thinking you mean this wording? In what episodes did the ENT-D's warp core threaten to, get threatened by, or actually did suffer a warp core breach?
Are you expecting "Contagion" to be added, because the ENT-D suffered from the same systems failures that directly caused the core breach on the Yamato?