Seth

Seth (セス Sesu) is a character from Street Fighter series, he makes his debut on Street Fighter IV as the main antagonist.

Profile
The CEO of the new military corporation "S.I.N.", responsible for the development of weapons for the criminal organization "Shadaloo". Seth's own body has undergone significant modifications. Along with the increase in his Ki from the "Tanden Engine" embedded in his abdomen, he is also installed with the data from a variety of martial artists, allowing him to make use of their techniques. In actually, he is one of 27 artificial humans created as replacement bodies for the leader of Shadaloo, M.Bison. He has a very logical personality, and will do whatever it takes to achieve his goals. He plans on capturing and analyzing Ryu for the sake of the BLECE weapon that he is developing, which if successful will artificially increase people's Ki.

Street Fighter IV: The Ties That Bind
Seth is first seen talking to a scientist about the experiment in the Amazon, wanting to make it commercially viable. Later, Seth discusses BLECE with Viper, revealing that BLECE is used to allow access to fighting energy, which is the reason why S.I.N. abducted the fighters, and are now after Ryu. C. Viper suggests that Seth come to see what Ryu is capable of personally.

In a cruise ship owned by S.I.N, Ryu is in a struggle with Seth, and losing. Seth speaks in length about obtaining ultimate power. Ryu realizes that the power he was looking for is not what he thought, and, indirectly through Seth's speech, found his purpose of seeking strength - to protect what is good and fight evil. Seth laughs and tells Ryu his speech is pure nonsense and attempts to attack him.

Ryu exhibits his new power, a result of rejecting the Satsui no Hado through his enlightenment (the same power Gouken uses and Ken used earlier, but even more powerful, his eyes glowing blue). His power burns the skin off of Seth's hand, and he defeats Seth with an unstoppable Metsu Hadoken, which burns through the android's muscles for a short period of time. After his defeat, Seth is rescued by S.I.N. members.

Seth is eventually cornered by Guile, Cammy, and the U.S Coast Guard. however, A Shadaloo helicopter picks up Seth, with Balrog and Vega on board, the latter of whom tells Seth that Shadaloo is the real manipulator.

Street Fighter IV
Seth is the 15th of at least 26 enhanced beings that use data collected from the world warriors to create a deadly style of mixed martial arts. Seth claims to be superior as a result of his humanity, while the others are merely puppets. His storyline indicates that he plans to control the remnants of Shadaloo through S.I.N. after M. Bison's apparent death at the hands of Akuma in Super Street Fighter II Turbo. He also attempts to use Juri Han, a woman who possesses the Feng Shui Engine in her left eye that his company created. She confronts him and unexpectedly offers to work for him, to which he agrees.

Seth hosts a World Warrior tournament in hopes of luring Ryu to him, and then using his Satsui no Hado to complete his BLECE project, but is dismayed at reports that M. Bison has once again returned from death. M. Bison finally encounters Seth and defeats him in combat, and afterwards tells him that in fact everything that has happened has gone according to M. Bison's plan. After M. Bison leaves, Juri tells Seth that she intentionally pitted the two against each other, but is disappointed that Seth was not more of a challenge for M. Bison. She then crushes his Tanden Engine, leaving him dead and twitching on the floor.

One of his brethren is found by C. Viper, who finishes him off. After the tournament, C. Viper informs her superiors that the "remaining 26" are in her sights. Whether this statement takes the final bosses encountered by all characters into account is not clear; Ryu encounters what appears to be another "Seth" and defeats him, destroying the BLECE machine as well. It is possible M. Bison may have commanded the remaining "puppets" to wreak havoc on the fighters in and around the S.I.N. compound, but it is implied that Juri destroyed most of them.

Street Fighter V
After the events of Street Fighter IV, the remnants of Seth's biological brain paired with the body of one of the Dolls, specifically Doll Unit Zero.

In their character story, Doll Unit Zero is activated by Juri, working on the behest of an unidentified party. Unexpectedly, the doll awakens with Seth's personality, much to her surprise. However the system within Doll Unit Zero alerts of systematic errors concerning the personality integration with the body, which results in Seth becoming mentally unstable and bent on finding and defeating Bison. Later, Seth confronts Ed and Falke, both of whom he mistakes for Bison, and fights them. Afterwards, Falke realizes that Seth was drawn by her and Ed's use of Psycho Power, making him see only the shadow of Bison. With this in mind, Falke and Ed leave, while the delusional Seth continues to claim his superiority.

Project X Zone
Seth appears as an enemy in the crossover game, Project X Zone, where he plays a major role in the game. Seth hacked Alisa Bosconovitch's systems to make her a weapon; he also took a V-Dural and mass produced it, creating four Dural stones. Seth also intended to destroy KOS-MOS to get her Vector technology (such act caused an enraged T-elos to join the player's party). With the bioweapons of Resident Evil, he created clone capsules, which were Nemesis T-Type to guard it.

Seth planned to take down Juri, retrieve the Feng Shui Engine and use her body as a core for Dural; he also sought not only to copy other characters' moves in order to "become an ultimate weapon", but also to capture Ryu and Jin Kazama to use their hidden powers (the Satsui no Hado and Devil Gene) in the BLECE. However, he was defeated for good.

In the last chapter, he is revived by the Portalstone, only to be beaten once more.

Street Fighter X Tekken 2: Return of Pandora
Seth appears as the Sub-Boss from Street Fighter side.

Street Fighter X Dynasty Warriors
Seth is one of the characters from Street Fighter side.

Capcom vs SNK 3: Fighters' Spirit
He is one of the characters from Capcom side.

WWE vs. Capcom
Seth appears as the Final Boss.

Project X Zone 3: War of Infinite Worlds
Seth appears as a Boss Unit.

Disney vs. Capcom: Infinity Requiem
Seth appears as an unlockable character from the Capcom side.

Trivia

 * Seth is the only character in the Street Fighter IV series who is capable of resetting juggle.
 * Due to his skill and his status, he is somewhat similar to Shinnok from the Mortal Kombat series.
 * Due to him being created by M. Bison sometime during Street Fighter II, Seth could be considered the youngest playable Street Fighter character.
 * Seth's business attire was also intended to be one of his alternate costumes, but ended up unused.
 * Seth is despised by many for his design, moveset and cheap AI. Producer Yoshinori Ono has even acknowledged the hatred, saying; "Everybody hates Seth, that's why he's back as the end boss in SSFIV. I want to torture people with him!" [...] "Seth will remain a target of universal hate".
 * Seth's appearance is very similar to Geegus, final boss from World Heroes.