The Tailed Beasts were created by Hagoromo Otsutsuki by splitting the Ten Tails into 9 halves, and then breathing lofe into them. They were all given names, and each Tailed Beast held specific powers. While there is no true measure of their Power Level, I’ve ranked them according to how I think they should be ranked.
Chomei, or Seven Tails, was not too great. It did have the ability to fly and all, but overall it’s strength isn’t comparable to the other Tailed Beasts. Chomei has the special ability to block chakra absorption.
Saiken, or the Six Tails, was pretty okay, compared to the rest of the Tailed Beasts. It has the special powers to produce corrosive acids that melt things within an instant, similar to Mei Terumī’s Kekkei Genkai.
Matatabi, or the Two Tails, was strong enough to fight against Gyuki during the Ninja War, but couldn’t do much else. It has the special ability to manipulate the Blue Flames, but nothing else is known about it.