Cruel Dragon

Cruel Dragon (, Zankoku Ryū) was a very ancient and powerful dragon that once laid waste to civilization before being weakened and sealed into nine stones. It was killed by Saitama.

Appearance
Cruel Dragon is a large, draconic monster with massive spikes protruding from its head and tail. It has three pairs of giant wings, four arms (six in the original webcomic), several rows of sharp fangs and three pupils on each eye.

Personality
Cruel Dragon is incredibly cold-blooded and sadistic, which is what lead to its namesake. Centuries of imprisonment increased its bloodlust exponentially and made it determined to wipe out humanity.

History
Long ago, Cruel Dragon rampaged and took a great number of lives. A group of ancient soldiers gathered together and although with great casualties, they managed to weaken and seal the dragon by separating its essence into nine stones. A cult known as Deathbone, which its people believe themselves to be dragon-born, since then attempted to collect the nine stones and release Cruel Dragon from its seal. Their opposing force, known as the Saints, prevented them from unleashing Cruel Dragon, with the antagonism having continued for eight hundred years.

The conflict between both sides appears to have come to an end when Cruel Dragon is finally eliminated by Saitama right after it is unsealed.

Monster Association Arc
During the fight between Saitama and Garou, as a result of a powerful attack from Garou, a temple with the head of Cruel Dragon is risen from under the sea.

Cruel Dragon Arc
Saitama accidentally gets in the middle of a battle between the Saints, a group of warriors dedicated to keeping Cruel Dragon sealed and Deathbone, a cult of "dragonborn" trying to release the monster by collecting all nine stones. After being explained the situation, Saitama decides to unseal Cruel Dragon so that he can defeat it and the Saints no longer have to worry about keeping him captured. Once Cruel Dragon is unleashed, it announces its intentions to destroy humanity before trying to attack Saitama. However, Cruel Dragon is then nonchalantly killed by Saitama with a single punch.

Abilities and Powers
Cruel Dragon's true power is hard to gauge due to its lack of a disaster level and how quickly Saitama killed it. It was definitely a highly dangerous monster, with its fire breath being able to scorch large areas of land in just a few days. Despite its great power, a large group of unknown soldiers managed to weaken it, though it cost them many casualties. The Saints were worried that Cruel Dragon would destroy all of humanity if it was unsealed.

Physical Abilities
Enhanced Strength: Due to its large size, it is very likely that Cruel Dragon boasts considerable physical strength.

Flight: Cruel Dragon possesses 3 sets of wings with which it can likely fly.

Supernatural Abilities
Fire Manipulation: Cruel Dragon can breathe fire from its mouth and scorch the surrounding lands.

Quotes

 * "The time has finally come... The hatred I have accumulated over the years... will be repaid with the lives of all humanity."

Trivia

 * Cruel Dragon is a reference to the storytelling trope of an ancient evil that has been sealed away and threatens to return, which is used in many classic stories such as the myth of Pandora's Box. This trope is subverted by having Saitama wake the evil up himself to just kill it and get it over with.