Adapting material from comics is always a tricky and somewhat shady process. Usually, most of the characters, settings, and themes will remain constant throughout the film but there's always the off chance that certain scenes, plot points, or characters in some spots will change.
This can be said about the incredibly surprising action spy comedy hit that no one saw coming Kingsman: The Secret Service and its subsequent sequel and an upcoming prequel that'll hopefully learn from the sequel's mistakes. Even though Kingsman manages to keep a lot of the content and ideas that the comic embodies and represents, there are still plenty of details that changed, some for the better and others not.
Glad Changed: The Big Exit
Typically, comics are large reaching in their length and size, with many a series running for a number of issues, ranging from fifty to even a hundred in length but every now and then, there are a few comics that are small in size, only six or so issues.
While the first volume was used for the first film, there were two other arcs that came out years later, that could've been incorporated into the sequel or spinoff but weren't, oftentimes, like with the forgettable "Big Exit" for the best.
Stayed The Same: The Red Diamond
However, while a one-shot like "The Big Exit" wouldn't have really worked for a two hour plus film, another story arc, "The Red Diamond", would or still could work. A strange yet entertaining arc that explores Eggsy in a great way, "The Red Diamond" could've been a cool arc to see on the big screen.
Unfortunately, the writers chose to go another way, choosing a convoluted drug plot of the sequel and a WWI for the prequel. Perhaps a third film could bring the "Red Diamond" to life. Maybe.
Glad Changed: The Villains
Funny enough, oftentimes the best villains for films end up coming from comics. Kingsman, however, like its unique story, works around this and allows for an even more unique and intriguing set of villains to appear.
Changing the first villain from being a professor to the eccentric and intelligent Richmond Valentine and allowing his henchman/woman Gazelle from a brash and trash-talking baddie to a silent killer was honestly one of the best things the film changed, even if the second film did struggle with Poppy and her fellow henchmen.
Stayed The Same: Gadgets
Every spy needs a gadget. It's what makes them who they are, defines them, and sets them apart from others. While anyone can be an international man of mystery, so few utilize gadgets and tools like James Bond or Ethan Hunt.
While Kingsman the film does have a collection of toys to play with, to the point of the Kingsmen having better gadgets than James Bond is some moments, the comics had way better ones. From a laser pen knife to a poison activated with the push of a button, the gadgets in the comics would've been way better and interesting than what audiences got.
Glad Changed: Harry Hart
In recent years, the super-spy Gallahad or Harry Hart, a suave and smooth-talking spy played perfectly by Colin Firth was one of the things that drew audiences into the film to see him take the young Eggsy under his wing and into one of the best spy organizations in film.
Yet, in the comics, Harry Hart doesn't exist. Instead of the super spy feeling guilty for Egsy's father's death, readers got Egsy's uncle recruiting him for... reasons. The idea of Harry Hart, however, carries the movie a lot more than Jack London could've.
Stayed The Same: Celebrity Prisoners
Having cameos in an interesting fashion pop up in a movie can just make everything seem so much better. While the film adaptation has Valentine kidnap and imprison multiple celebrities, audiences never really see anyone past the Princess of Sweden.
Even Elton John popping up in the sequel wasn't as good as David Beckham cheering on Eggsy or Pierce Bronsan arming himself with a machine gun to take on the bad guys. Those kinds of cameos could've boosted an already great film to an even higher spot.
Glad Changed: The Uncle Connection
It's worth noting that the Uncle Connection that the comics bring up isn't exactly as strong as the Harry Hart one in the film. Harry Hart has a need to bring Eggsy in, a debt he feels as if he owes that adds to his character and guilt.
Jack London(Yes, that's his real name) doesn't have such qualms. London really only recruits Eggsy because he's his nephew and dies a rather disappointing death, being shot in a hotel room instead of dying outside a church full of crazed people in an incredibly well-thought-out one-shot take action scene.
Stayed The Same: Recruit Teamup
There's something just heartwarming about a group of individuals coming together to fight as one. In the film version of Kingsman, one of a number of comic book adaptations that aren't about superheroes, viewers get this in the form of Merlin, Eggsy, and Roxy taking on their own challenges separately to take down Valentine.
In the comic though, the team-up is a little more heartwarming, with Eggsy rallying his fellow recruits to go take down the mad Professor. What follows is some good-natured spy craft mixed in with some awesome R-rated goodies that make the comic a classic.
Glad Changed: Mark Hamil
Yes, this is a real thing that was in the comics. The first Kingsman comic opens with an agent breaking into a secure location and saving Mark Hamil, the celebrity, from capture, only for both of them to suffer darkly humorous deaths.
That being said, while Mark Hamil shows up in the film, he's not playing himself but instead a scientist named James Arnold. Keeping Mark Hamil present for the movie but giving him another role that pushed the plot forward rather than serving as a joke benefit's the film.
Stayed The Same: Ending
Let it be said that ending a film is easier said than done. Having all the threads connect in the right way has to be pulled off perfectly in order for a movie to end properly.
While Kingsman does have a great ending, with Eggsy saving the day and becoming an agent, the comic's ending was a little better. It brought all the recruits together in a heartwarming finale and beat the bad guys by changing the signal so everyone got intimate instead of tearing themselves apart. Now that would've made one of the best spy comedy films even better.