"Die with honor, O'Brien."
— Tosk, Captive Pursuit
Similar to this question, how many times in Star Trek is Chief O'Brien showed or implied to die?
On Deep Space Nine, O'Brien dies (or is implied to be dead) seven times.
In "Armageddon Game," O'Brien and Bashir are presumed to be dead when T'Lani surveillance shows them being wiped out by a radiation flash from a weapon they were trying to disarm. It turns out that the video footage was faked.
In "Whispers," the Miles O'Brien who is the central character of the story turns out to be a replicant created to assassinate an alien dignitary. He is shot and killed before he can carry out his mission.
In "Visionary," O'Brien jumps forward in time a few hours and witnesses his future self being killed by a booby trap on a Klingon listening device. He returns to his own time and avoids that fate.
On another jump into the near future, he learns that his future self died of radiation poisoning, but Dr. Bashir tells him the medical procedure he needs to use in order to save his life when he returns to his own time.
On his last trip to the near future, O'Brien realizes that he is dying of radiation poisoning again because of all the time travel, so he tells his future self to return to the past in his place.
In "Distant Voices," Bashir is trapped within his own mind because of a psychic attack by a Lethean. Various aspects of Bashir's personality are represented by people he knows, including O'Brien, and each of them is killed by the Lethean as Bashir's mental condition worsens.
In "Children of Time," the crew of the Defiant encounter a colony populated by their own descendants created when the Defiant leaves the planet, travels back in time, and crashes two hundred years in the past. In that timeline, O'Brien (and most of the crew) died many years ago.
Then the ship leaves and fails to crash, wiping the colony from existence. Since you could arguably treat this as either two deaths or zero depending on how you look at it, I'm going to split the difference and count it as one.
This number goes up by a lot if you include Star Trek: The Next Generation, thanks to "Cause and Effect," in which the Enterprise is caught in a time loop in which it is destroyed again and again, probably dozens of times. O'Brien isn't in the episode, but it takes place in season 5, which is before he transferred to DS9.
Add one more for the past version of the Enterprise being destroyed in the TNG series finale, "All Good Things...", in which O'Brien does appear.
Did I miss any?