Sensei

The Sensei is a fictional character in DC Comics' shared universe, the DC Universe. He is a martial artist and sensei created by writer-artist Neal Adams as a villain to fight the hero Batman. He first appeared in Strange Adventures #215 (October 1968).

History
Ra's al Ghul may have founded the League of Assassins, but he would leave much of its affairs in the hands of Professor Ebeneezer Darrk and his second in command: the Sensei, an aged martial arts master from Hong Kong. After earning Ra's enmity (for reasons unknown) Daark died during a plot to kidnap Talia al Ghul which was foiled by The Batman.

His rise
The Sensei was put in charge of the League afterwards, however he would prove just as disloyal as his predecessor, and the Sensei would eventually struggle with Ra's al Ghul for the control of the organization. For a time, the Sensei was possessed by the spirit called Jonah, who in Sensei's body was responsible for the murder of Boston Brand, who became Deadman after his death. After a struggle with Deadman and Rama Kushna, Jonah was destroyed and the Sensei resumed control of his body. For a brief time, the Sensei assumed leadership of the League of Assassins.

His Insanity
By this stage, the Sensei was clearly insane (if he had not been before) with no goals other than to raise assassination to an artform. Among other crimes he used Bronze Tiger, the brainwashed partner of Richard Dragon, to carry out a number of assassinations. Most notably he used the Bronze Tiger to occupy Batman in battle, while other assassins killed Batman's friend Kathy Kane.

His fall
He next attempted to kill a number of dignitiaries by having the League plant explosives along a fault line, stating that using a force of nature to carry out an assassination would be his greatest work of art. Although Batman arrived in time to rescue the delegates, he was unable to stop the earthquake. With no time to pursue the Sensei himself, Batman was forced to allow Ra's al Ghul to go after the assassin. Sensei then engaged himself in a fight to the death with Ra's al Ghul, during which both of them were swallowed by the earthquake. Ra's lived thanks to his rejuvenating Lazarus Pit. The Sensei also somehow survived, to reappear in the "Batman: The Resurrection of Ra's al Ghul" storyline, wherein he is revealed to be al Ghul's father.

In other media
The Sensei appeared in the comic book Batman: The Gotham Adventures (based on Batman: The Animated Series). Unlike his counterpart in the mainstream DC Universe, this version of the Sensei was directly responsible for the murder of Boston Brand, creating the ghostly hero Deadman. In the comics, the Sensei had an operative named the Hook kill Boston Brand.

The Sensei served the Ra's al Ghul of the animated series, training assassins for the immortal's use. After being tracked down to the League's headquarters in Tibet, the Sensei engaged both Batman and Batgirl in combat, and was apparently defeating them when the battle was broken up by Ra's and Talia. Ra's required Batman for his plans, and when Batman refused to leave without the Sensei, Ra's ordered him to go with Batman. Neither wishing to get in the way of Ra's plans nor to spend the rest of his days in prison, the old man chose a third option and quietly walked out one of the windows of his mountain hideaway, falling to his death.

In Batman Begins, an old man that lives nearby the headquarters of the League of Shadows resembles to the look of the Sensei. After Bruce saved Ducard's life and takes it to this old man, he says that he will tell Ducard that Bruce saved him.