Gen is (or was, depending on if he is dead in the canon or not) one of the strongest characters to exist in the Street Fighter franchise. He made his first in-game debut in the original Street Fighter, and was not seen again until Alpha 2. An assassin by trade, Gen trains in the Ansatsuken styles of kung-fu, which basically is a fancy way of saying he trains to kill people. He incorporates many styles into his technique, including Bear, Mantis, Crane, and others. Gen is also one of the oldest characters in the franchise, apparently being born before 1918. Ergo, he has multiple connections to other characters. He was a friend of Chun-Li's father and actually trained her as a child, and also raised both Yun and Yang (although he is not their father, contrary to popular belief). These links are confirmed throughout the franchise, as dialogue in Alpha 2 shows he gave Chun-Li the tip on Shadowloo, and both Yun and Yang use very similar fighting styles based on Gen's two stances used in the Alpha games. Although an assassin, Gen is not an inherently evil character. His only motivation for joining the first World Warrior tournament was to find worthy opponents, and his entry in the Alpha series was similar, the only difference being that this time he was actually dying from disease, and wanted to die in combat. Gen also possesses one of the strongest super moves in the SF canon: the Zan'ei.
Gen was the only fighter in all of Street Fighter that was able to change stances mid-battle. His crane style was faster, yet weaker, while his mantis style sacrificed speed for damage. The ability to juggle the two stances as needed made Gen an absolute combo machine. As previously stated, Gen possesses the Zan'ei, a super move in which he slides through his enemy, leaving them in a combo of damage on the other side of the screen. It is somewhat similar to Akuma's infamous Shungokusatsu, which explains their rivalry in power.
Street Fighter Alpha 2
The defeated Akuma insists Gen finish him off, but the elderly fighter decides to spare him leaving him to his fate. On his way home, Gen feels he might lose his joy in fighting if he were to kill Akuma; But when his illness begins to take its toll, Gen decides to die fighting.
Gen's Win Quotes
" Your fate is sealed. There is no escape now. "
" We begin dying the moment we are born. There is no escaping this truth. "
" You are unworthy of my attention. Leave my sight at once! "
" Death is a bitter medicine we must all drink. I do not cower before it. "
" My only fear is that I shall pass before my appointed fight to the death. "
" The sight of blood makes me feel young again. "
" Your weakness is an embarrassment! "
" This is no place for the likes of you. "
" If the prospect of death frightens you, leave this place at once! "
" You are a big fool! "
" What immaturity! "