My understanding of the psychology of revenge has always been very simple: if you are wronged and do nothing about it, the perpetrator and everyone else who learns about that may get tempted to wrong you again when given an opportunity. In other words, the goal of revenge is to build a reputation of a revengeful person and thereby deter people from doing injustice to you. Sure, people seeking revenge don't always clearly think in such rational terms, but they are at least driven by the vengeance instinct, which survived in us because of, I think, the evolutionary benefit described above. So I think that the vengeance instinct is normally triggered only when the desired revenge is subconsciously felt to be likely to produce a useful deterrent effect.
However, I watched quite a few famous movies in which the main character embarks on a very dangerous and costly revenge-seeking mission that can't really be explained in terms of deterrent effect and has no other personal benefit worthy of undertaking the mission. For example, in The Godfather Part II, the don of a crime family in America travels to Italy to exact his childhood vengeance from a Sicilian local mafia chieftain and almost gets killed there. In Lady Dragon, a CIA agent resigns from her job and goes to Southeast Asia in a pursuit to kill the drug lord she suspects ordered the killing of her husband, and there she gets raped and almost gets killed. In Licence to Kill, James Bond turns down an important assignment and becomes a rogue agent to get revenge for his friend, who lost his wife and a leg, from a drug lord who is powerful enough to control an entire country in Latin America. It seems highly irrational for the main characters of such movies to risk their own lives and waste so much time and effort just to seek revenge for no personal gain worthy of engaging in such pursuits.
What is the view of modern psychology and neurology on people like the main characters of the above movies? Are they considered to be vengeful psychopaths despite being positively portrayed in movies, or is it considered normal and justified to get seriously distracted from life goals in order to seek revenge even when there's no direct or indirect personal benefit of it from the rational standpoint?
A friend of mine opined that the vengeance instinct is a somewhat outdated instinct we are all born with and that this instinct possibly renders taking revenge the only possible way to fully regain psychological well-being after a particularly traumatic experience. Regaining psychological well-being, in turn, helps achieve life goals. I'm curious whether this kind of reasoning to justify seemingly pointless revenge-seeking missions is backed by science.