Given the chance, I don't think I would behave in any enlightened or merciful manner in the act of real emotional vengeance.
I'm just getting to bed and browsing r/wtf after an intense evening with my mother, who is currently visiting from Israel and staying with my sister and I, (we are near the middle of a total visiting period of just over two months). I'm a little high currently, and feel like sharing.
One of the themes my mother and I went into in our conversation tonight was an identification and imagination of certain grave acts. She related the story of her father's, (a holocaust survivor), who had the strange fortune of being one of few German speakers in a small non-German speaking place following the end of the war by a year or two, (details are murky at the moment, limited to my current recollection and understanding and incomplete information, though the period of time given is my best guess informed by other details.)
After a several month nursing and recovery from Typhus following the end of the war, and his following reconnaissance tour of his home town and other areas, my grandfather was called in to a local gendarme's station to help interrogate two captured SS. By that time he had pieced together the fate of his sisters and mother who were killed in early May, 1945. He had discovered through re-connection with two uncles, an aunt, friends/neighbors/school mates/and cooperative local outposts., that his mother and sisters had been party to a massacre of 223 Hungarian Jews, forced to dig their own grave pit, then shot into it and set aflame with (petroleum spirits of some sort...) in Persenbeug, Austria.
Like something out of a movie, my grandfather realizes that the two SS he is interrogating were also at this party.
At this point I have to state that this story is based on my mother's recollection of an interview in print that my grandfather made in the late 1980's. A translated transcript will be forthcoming within the next week or two, (this is a project my mother almost asked for help on earlier this evening, and I find myself likely to volunteer).
The story goes that my grandfather asked the local authority if anyone would miss either of these captives, and was in turn given a vehicle of some sort, two shovels, a loaded firearm, and custody of the SS, and that he took them into the country side, had them dig their graves and executed them.
My point of identification with this part of the story is that, if I'm honest with myself, given similar circumstances I might give in to something vicious inside of myself and really stretch out the experience in the subject of my torture. (My mother and I both are both guessing (biased with our discomfort for other possibilities) that he shot them cleanly, feeling that the act of digging their own graves might have been torture enough...)