Villains are some of the hardest things to get right in a movie. It's easy to make a hero. Throw some people in danger, have someone step in and save them and boom, you've got a hero. It obviously helps if the hero's journey is a tad more complex than that, but at bare minimum they need to just do the right thing.
It's not the same with villains. Doing the wrong thing isn't sufficient enough to make for a truly great villain. You have to understand where they're coming from. There has to be an unsettling logic to their plans, to the point where the audience almost sympathizes with them. That is one of the many, many things Kingsman: The Secret Service did right. Samuel L. Jackson's Valentine is a bad guy who is not only fun to watch, but he's one with an evil scheme that's both psychotic and understandable: Planet Earth has a fever in the form of mankind and the only way to combat the fever is to reduce mankind to a manageable temperature.
Of course, as is the case with almost all movie villains, Valentine's plan did not go as expected (stupid heroes always getting in the way) and so he's not going to be around to menace the Kingsman in a sequel. That leaves some big shoes to fill, but thankfully the producers have found one of the most exciting actors on the planet to rain down villainy this time around. According to THR, Fox is currently doing the paperwork to get Oscar winner Julianne Moore to play the big bad in The Kingsman 2.
We have no idea who this villain is or what her plan will be, but recently star Taron Egerton confessed the new villain not only rivals Jackson's, but is "so brilliant written I wish I could play it. It's amazing."
This news does come with a bit of a sad caveat, however. THR also reports that Colin Firth will definitely not be returning for the sequel. Apparently the production had concocted a few ways to bring him back, including by having him play his own twin brother, but they're all off the table now. Even still, we trust that Matthew Vaughn knows what he's doing and that The Kingsman 2, which is the first time he's directed a sequel to one of his own movies, is going to be just as fun, funny and ridiculously entertaining as the first movie.