This article contains spoilers for Legion of X #3.
The X-Men's new enemy, the Skinjacker, proves difficult for Marvel's mutants to defeat, but he would absolutely destroy the Avengers. The X-Men and the Avengers are two of Marvel's longest-running superhero teams. Unfortunately, the relationship between the two hasn't always been especially good - there have been multiple "Avengers Vs. X-Men" stories, sometimes on the most spectacular scale imaginable.
The X-Men tend to have one major advantage over the Avengers: the fact they have so many different telepaths. For years Professor X was considered their most powerful psychic, literally able to stun most enemies with a single psychic blast, but nowadays he's been exceeded by Jean Grey. Jean is an Omega-level telepath whose connection to the Phoenix Force means she wields power even Thor cannot resist, while her telekinetic fields have protected her from some of the most destructive forces in the Marvel Universe. Emma Frost may not pack as much of a punch as Jean, but she's a skillful telepath who knows how to get around her enemies' defenses. Most "Avengers Vs. X-Men" battles have involved the Avengers trying to neutralize the X-Men's psychics as quickly as possible, because otherwise they'd be swiftly defeated.
This also means the X-Men routinely face enemies who would destroy the Avengers. Take, for example, the Skinjacker - an enemy plaguing the X-Men in Si Spurrier and Jan Bazaldua's Legion of X series. This mysterious being has the ability to possess the bodies of others, and he's proving a difficult enemy for the X-Men to fight, only beaten when the mutants arrange a psychic trap for him. It's a tactic the Avengers would be unable to deploy, simply because they don't tend to have telepaths at their beck and call.
The trap is a smart one, though unlike Skinjacker, readers will immediately know something is wrong when Doctor Strange appears to arrive on the island of Krakoa. Doctor Strange has recently been killed in the Marvel Comics universe, passing on the role of Sorcerer Supreme to his wife Clea. It turns out to be an artificial body, and once Skinjacker is trapped inside this host he's telepathically trapped. Most Avengers teams would struggle to duplicate this tactic.
It's fascinating to imagine the chaos Skinjacker could cause if he possessed Avengers rather than X-Men. He'd be a true force to be reckoned with if he took over the likes of Thor and the Hulk, or if he used Captain America's body to maneuver himself into a position of authority. Worse still, the Skinjacker seems to be able to access the memories of his host bodies, so he could discover any number of long-hidden Stark weapons if he took Iron Man. The Avengers can be thankful Skinjacker has headed to Krakoa to face the X-Men rather than focusing in on Earth's Mightiest Heroes.