The Secret Service
Valentine's (Samuel L. Jackson) plan is to use the SIM cards he distributed to the world to emit a frequency that will drive the population insane and make them all kill each other. Valentine convinces many of the world's leaders to agree to be protected via an implant in their necks, which can also be detonated in case things go wrong.
Harry Hart (Colin Firth) witnesses firsthand the power of the frequency when he is caught in Valentine's test range at a hate church and singlehandedly kills everyone inside. Valentine meets him outside and, rather than explain his plan like a typical villain, shoots him in the face.
Eggsy (Taran Edgerton) teams up with Roxy (Sophie Cookson) and Merlin (Mark Strong) to assault Valentine's base in the mountains. They activate the kill switches in the neck implants, killing everyone under Valentine's sway and disable the frequency, saving the world. Eggsy kills Valentine and takes over Hart's role as Galahad in the Kingsmen.