The Eternity Devil can manipulate time in certain places. Time does not move wherever it resides.
As it attacks using typhoons, its area of damage is so wide that its attacks affect not only its enemy but also civilians.
Akane has a contract with the Snake Devil. It has the ability to absorb living things.
Mysteries surround her. Since we cannot measure her true power, it is safe to give her a lower ranking until further information is given.
Be it strength or an outstanding swimming ability (even on land!), he has it all. His crazy endurance also makes him difficult to handle.
She is the Spider Fiend. Personality-wise, there is not much to say about her.
Her Ghost Devil is indeed immensely powerful. It can vanish, thus being able to attack swiftly without being seen or touched.
His strength is absolutely brutal, with him being able to destroy almost everything with a single punch or kick.
Katana Man is far from weak. In fact, he is the first villain who managed to push Denji beyond his limits.
As a Blood Fiend, Power has the ability to manipulate blood as she wishes.