"You don't know how many times I wished I was."
Survivor guilt or survivor's guilt was a psychological disorder where a person feels guilty for surviving a traumatic experience or blames themselves for something they did wrong that caused the death of others.
Following the death of Captain Garrovick and nearly half the crew of the USS Farragut by a dikironium cloud creature, Kirk felt terrible guilt over his captain's death. Years later, Kirk admitted that "I could have killed that thing if I'd fired soon enough the first time"; however, Doctor Leonard McCoy attempted to dispel Kirk's guilt, which was bordering on obsession, assuring him, "You don't know that, Jim." (TOS: "Obsession")
In 2267, Commodore Matt Decker experienced survivor guilt after he beamed the entire complement of the USS Constellation to the third planet of the System L-374 only to have the entire planet destroyed by the planet killer. (TOS: "The Doomsday Machine")
In 2366, the crew of the USS Enterprise-D discovered that Kevin Uxbridge was the only survivor of the attack on Rana IV by the Husnock after he perpetrated a deception to try to get them to stop investigating the events of the attack. After he stated that he had destroyed the Husnock in his grief, Doctor Beverly Crusher asked him why he had revealed this to them now, if it was guilt for not helping the colonists to defend against the attack. He, however, explained that she and the others did not understand the scope of his crime, that he had not merely destroyed simply one Husnock warship in his anger, but had in fact committed the genocide of the entire Husnock species. (TNG: "The Survivors")
Lieutenant Commander Benjamin Sisko experienced survivor guilt after his wife Jennifer was killed during the Battle of Wolf 359 in 2367. The guilt defined his existence until he had his first encounter with the Prophets in 2369. (DS9: "Emissary")
Timothy, a young boy on the SS Vico, experienced survivor guilt following the death of his parents in 2368. In an effort to deal with his guilt, Timothy briefly declared himself an android and modeled himself after Lieutenant Commander Data. (TNG: "Hero Worship")
Beckett Mariner experienced severe survivor guilt as a result of the Dominion War breaking out and surrounding her with death and destruction before she could fully recover from Sito Jaxa's death. As Sito was never promoted beyond Ensign and Mariner had become afraid of giving orders that would result in a friend's death, the guilt resulted in a cycle of erratic and self-destructive behavior as part of a deliberate effort to stall her own career at that rank, leading to recurring demotions to the point where she was in danger of facing court martial. These demotions lasted until 2381, when Commander Jack Ransom realized that she was intentionally getting herself demoted and refused to allow her to continue self-sabotaging. However, with the root cause not addressed, her self-destructive behavior continued, even escalating to suicidal levels, until she disclosed her trauma to Ma'ah while both were stranded on Sherbal V and he told her that Sito would never approve of her actions. (LD: "I Have No Bones Yet I Must Flee", "The Inner Fight")
In an alternate timeline, when Chakotay and Harry Kim successfully returned to Earth in 2375, via Quantum slipstream drive aboard the Delta Flyer, at the cost of the loss of the USS Voyager, Kim experienced the profound effects of survivor guilt, also to the point of obsession. Kim's counselors at Starfleet Headquarters told him "You must learn to accept the fact that you lived. Embrace life, move forward."
In 2390, while in discussion with The Doctor, following his reactivation, about the occurrences of the past fifteen years, The Doctor pointed out that "I suppose it must have been difficult, with all your friends and colleagues left behind." Kim caught on to what The Doctor was getting at, he recalled the diagnosis, but still did all he could to undo the wrong he did. Upon finally correcting his mistake, Kim left a message to his past self-explaining, "Fifteen years ago, I made a mistake and one hundred and fifty people died. I've spent every day since then regretting that mistake, but if you're watching this right now, that means all of that has changed. You owe me one." (VOY: "Timeless")
Captain Liam Shaw experienced severe survivor guilt following his survival of the loss of the USS Constance at the Battle of Wolf 359, having been randomly selected, along with nine others, by a lieutenant to board the one remaining escape pod. The trauma of the battle and the survivor's guilt would follow him for the next thirty-four years, ultimately culminating in him confronting Jean-Luc Picard for his role in the battle aboard the USS Titan-A in 2401. (PIC: "No Win Scenario")
In 3190, Dr. Kovich assessed Dr. Hugh Culber's savior complex at getting a second chance at life as a form of survivor guilt. He described Culber's need to feel a purpose as thinking that if he did not have one that his very existence was a middle finger to anyone who had ever lost anyone, which was everyone. He further told him that it was how he escaped his persistent guilt of being alive and that he needed to find a purpose in something other than work or he would fail those in the chair in front of him. (DIS: "The Examples")