This article contains spoilers for Sabretooth #3.
The X-Men's Sabretooth proves he's an underrated villain - by launching an insurrection on Krakoa even though he's a prisoner. Sabretooth is often considered Wolverine's twisted mirror image; Wolverine is the man who fears he's really a beast, whereas Sabretooth considers himself a man who revels in the savagery of the animal within. He was the first mutant considered to be irredeemable by the leaders of Krakoa - a pretty remarkable judgment considering they have forgiven the X-men's worst enemies like Apocalypse and Mister Sinister.
In truth, there was no justice to Sabretooth's sentence. He was sentenced for the crime of killing a human, even though the laws of Krakoa hadn't been decided yet. But Krakoa's ruling Quiet Council knew he'd be trouble, and so they banished him to a psychic prison deep beneath the island. They had no idea his mind would take control of the environment, and so as they banished other criminals into this pit, they unwittingly stranded them in a realm Sabretooth controlled.
Worse still, he is learning to influence the real world, and in Sabretooth #3 by Victor LaValle, Leonard Kirk, and Rain Beredo, he reveals the full scale of his plan. The X-Men have forgotten Sabretooth is more than just an animal. Like Wolverine, Sabretooth's mutant healing factor means he's had an unusually long life. His unique skillset has drawn the attention of countless black ops organizations, and he even worked for Nick Fury as a member of a proto-Avengers team at one point. In Sabretooth #3, Victor Creed uses a trick he learned from the CIA; to send his fellow inmates into the real world as so-called "soft-liners," secretly undermining the leadership of the Quiet Council. The genius of Sabretooth's strategy lies in the fact they don't even know he's using them, proving Sabretooth is so much smarter than the X-Men realize.
The irony, of course, is that there's a sense in which Sabretooth is right to distrust the Quiet Council. The members of this ruling body appoint themselves, with not even an attempt at democracy and accountability; they keep many secrets from the rest of mutantkind, putting them all at risk. Ironically, this means many mutants on Krakoa instinctively distrust them, sensing the Quiet Council wield far too much power. As Thomas Paine put it, "A body of men holding themselves accountable to nobody ought not to be trusted by anybody."
The Quiet Council have underestimated Sabretooth after he vowed revenge on the X-Men. They're paying a fearful price for doing so, because he is preying upon their weakness from the shadows, undermining them and encouraging those who already doubt their judgment. But, of course, this will only be the beginning of Sabretooth's plan; he is far more than just a savage, and his ruthless cunning has the potential to bring the X-Men's leaders down.