Grendel

Grendel is an Evil Dragon, known as the Crime Force Dragon and a member of Qlippoth.

Appearance
A dark green Western Dragon with silver eyes. Unlike other Dragons which are usually seen on their four legs, Grendel stands on his hind legs like a human. Issei claims that he is closer to a giant with the features of a Dragon.

Personality
Grendel is an aggressive, psychotic Dragon that is only interested in fighting and killing. He is a battle maniac who loves physical combat and destroying more than anything. He is also very resilent. It is also implied that he may enjoy pain as he shows his sadistic joy when he receives more pain.

History
In the past, Grendel also fought against Ddraig at some point before he was sealed. He was later slain by the original Beowulf, but was later revived by the Khaos Brigade sometime before Volume 14.

The Legend of Oppai Dragon and his Lively Companions
Grendel appears in Volume 14 alongside Euclid Lucifuge and fought against Issei Hyoudou one-on-one until Euclid orders him to retreat as the two left to where Vali and his team were at.

In Volume 15, it is revealed Grendel, upon arriving at Vali's location, ended up quarreling with another Evil Dragon, Aži Dahāka, allowing the Vali Team to escape.

In Volume 16, he appears before the Occult Research Club while they were on the way to retrieve Valerie. After a fierce battle Grendel loses with only half of his head remaining due to taking on Rias' new finishing move, Extinguished Star. He was forced to retreat after Crom Cruach commandeers the fight.

In Volume 17, Grendel appears at the southwest region of Agreas together with Ladon. He fought Saji and some of the fathers of the children but they were defeated easily. Before Grendel could deal more damage to them, Sairaorg arrived and took him as his opponent. He and Ladon where then ordered to retreat but Grendel refused to go back and decided to fight Sairaorg and Issei head on alone. With Sairaorg using the Balance Breaker of Regulus and Issei using True Queen, they were able to overwhelm Grendel up until Walburga appeared and deal considerable damage to Sairaorg using her Longinus, Incinerate Anthem. But even with Sairaorg's injuries, he and Issei were able to take down Grendel with Issei using Crimson Blaster and Sairaorg dealing the final blow. Koneko then used Shirone Mode to seal Grendel's soul inside a jewel from Issei's armor.

Power and Abilities
Immense Defense and Endurance: His Dragon scales are considered as one of the hardest and toughest scales out of all Dragons which is shown when he was able to take a punch from Issei in his Welsh Dragonic Rook form without substantial injury (aside from some blood from his mouth).

Immense Durability:  He also went as far as to claim that he didn't feel a thing and that Issei was weak. He is highly resilient to physical pain, allowing him to continue to move and fight despite grievous injuries. His enhanced durability allows him to resist more damage than a regular Dragon.

Immense Strength: He is also shown to be physically strong as his normal punch was described by Issei to be more powerful than Sairaorg Bael's punch in his Balance Breaker form, Regulus Rey Leather Rex.

Immense Speed: Despite his size, Grendel is shown to possess great speed.

Dragon Flames: Like most Dragons, Grendel can also breathe fire.

Trivia

 * Grendel is the only known Western dragon that stand on two legs.
 * Grendel is described by the author to be like Kamen Rider Ouja from Kamen Rider Ryuuki.
 * Grendel has blue blood.