Deathlist, published by Chris Ryan in 2016, is mainly about disgusting people being killed in disgusting ways. I did read it, skimming in parts, but I can’t say that I enjoyed it. For those who aren’t attracted by the disgusting aspects there is a straightforward plot (at least until the very end) of soldiers taking revenge on terrorists who assassinated a bunch of special forces trainees at an exercise in England, including details of how the perpetrators were captured and all vehicles and weapons involved. The book doesn’t have much else to recommend it, since the avenging soldiers are great at killing and torture but are worthless in the conversation department.
At first glance the personalities of the avengers might seem realistic, but I’m not sure that’s the case. My counter example is a book I read years ago by a retired British mercenary whose name I can’t remember. He had to leave his special forces unit ( I think he wasn’t great at following orders) and spent some years as a mercenary, during which time he trained soldiers in various Middle Eastern and African countries and also was hired by some governments for other purposes. On one of his missions he was one of a group hired to capture or kill (I don’t remember which) a Basque terrorist the Spanish government was anxious to be rid of but wanted to distance itself from the ridding. His memoir was fascinating and very well written and although he doesn’t come across as a “nice guy”, he’s a far cry from the thuggish bunch presented by Ryan.