After spending years in development as one of the first Marvel Studios project, Ant-Man finally arrived in the summer of 2015, only a few months after Avengers: Age of Ultron. In his origin story, Paul Lang's Scott Lang faced off against Corey Stoll's Darren Cross, a.k.a. Yellowjacket, Hank Pym's former mentor who built his own shrinking suit, albeit to be used as a weapon. Like many of the Marvel Cinematic Universe's villains, Yellowjacket basically served as a twisted counterpart to Ant-Man, and director Peyton Reed acknowledges that ultimately he wasn't a fan of how the main antagonist turned out. Reed explained:
The villain in that movie felt like a bit of a vestige from the era in which that project was started, [which was] around the time of Iron Man one, where you have an antagonist who has a similar power set [as the hero]. I was hell bent on doing something different in [Ant-Man and the Wasp].
Ever since Obadiah Stane built his Iron Monger suit in Iron Man, the movie that kicked off the MCU, this franchise has had a habit of pitting its heroes against villains with similar skill sets, with other examples including Hulk and Abomination, Captain America and Red Skull, and Doctor Strange and Kaecilius. Some of those kinds of villains have been well-received, others haven't, and as Peyton Reed acknowledged to io9, he feels Yellowjacket, who he inherited from Ant-Man's Edgar Wright and Joe Cornish days, ultimately didn't pay off as a baddie. If it helps, at least Yellowjacket has been taken off the table for good, as Darren Cross' body was crushed by his out of control shrinking suit when Scott Lank shrunk and damaged its internal mainframe.
Fortunately for Ant-Man and the Wasp, this particular villain problem wasn't an issue. This time around, Scott Lang and Hope van Dyne (who is finally suiting up) are facing off against the mysterious Ghost. While her background is still shrouded in secrecy (with one notable exception), the previews have shown her using her phasing abilities. It's one thing fighting an adversary who as similar abilities as you, but going up against someone who you can't even touch is arguably even more challenging. Throw in Hank and Hope recruiting Scott to help them find Janet van Dyne in the Quantum Realm, and our intrepid protagonists have a lot to deal with in this latest Marvel movie.