Sergei Dragunov

Sergei Dragunov was introduced in Tekken 5: Dark Resurrection, and has returned to every subsequent games. Sergei Dragunov is a member of SPETSNAZ, the military headquarters responsible for investigating the unknown body. They thought of giving special orders to one man involved in the excavation. A man named Dragunov, a member of the Special Forces, the very symbol of fear on the battlefield who has been dubbed "The White Angel of Death" because of his overwhelming fighting prowess.    

During the King of Iron Fist tournament 5 (Tekken 5 DR) Dragunov was sent into the tournament to find Devil Jin and bring him back to Russia. However during the tournament Dragonuv lost Devil Jin and failed his mission, returning to Russia empty handed. 

During the events of Tekken 6 the war raging on between the Mishima Zaibatsu (headed by Jin Kazama) and G Corporation (Headed by Kazuya Mishima) and the unrest that the war caused, Dragonuv was given orders by Russian high command to infiltrate the Mishima Zaibatsu and to crush them single handedly.

Endings:

Dragunov's ending has him bringing back Devil Jin to Russia and allowing Russian scientist to perform an unnamed test on him while he remains floating in a tank of fluid.  During the test, energy is transferred to another tank carrying an unidentifiable character/monster which after the energy transfer is complete awakens.
(It has been rumored to be Ogre or Azazel on numerous occasions. Although this has not been confirmed nor in his ending canon in the series)
His ending can be seen here - http://www.youtube.com/watch?v=vS334cGUWFY
In his Tekken 6 ending the Russian army have ceased Azazel's body, but out of nowhere Raven shows up on a plane.  He then extracts the orb and tries to escape.  As Raven is being shot at by the Russian army, Dragunov slips a charge on his plane and detonates it.

Trivia:

• Dragunov has the unique characteristics in that he is only one of two characters to not speak any audible dialogue along with Armor King during the Tekken series. (King, Mokujin, Roger/RogerJr and Kuma/Panda do not speak words but have subtitles indicated some form of speech with other characters during cinematics).
• Dragunov was actually a character design that was going to be used during Tekken 3 but was scraped and replaced by newcomer Bryan Fury.
• Dragunov using the fighting art known as Sambo, his character has numberous locks and throws off of moves that when hit, they switch into his throwing arts.
• Dragunov shares his special mounting ability with Craig Marduk in that he does not do mounted punches as other characters can when tackling the opponent.
• Dragunov's name is based on two russian sniper gun designers, Sergei Simonov and Evgeny Dragunov.
• His name may also be based on a famous Sambo practitioner, Sergei Kharitonov.
• Although silent save for grunts in the game, an interview with one of the creators of the Russian character revealed that Dragunov is perfectly capable of speaking, just that he doesn't want to, and that he also enjoys singing outside of battle.
• Before Dragunov fights Devil Jin during his Stage 8 encounter, he looks at a picture of his opponent. It appears to be a picture of Devil Jin in his complete transformation (see Devil Jin's Tekken 5 ending). Also, after Dragunov defeats Devil Jin, Dragunov can be seen dragging an unconscious Devil Jin by the horns.
• It is unknown what is the entity in his Dark Resurrection ending; speculation leads the entity to be Azazel or Devil Kazuya, but paying particular attention to the ending section of the clip, is possible to note a similarity between its silhouette and Jinpachi's. This may mean that the model of Jinpachi was used for the entity, but not that it actually is Jinpachi in terms of storyline, since it was kept unrecognizable.    
• He was potrayed by Anton Kasabov in the Tekken 2010 film.