Lightning Group

The Lightning Group was a group of disenfranchised shinobi, most of whom possessed a kekkei genkai. The group was first formed by Fūshin and other former slaves of En Oyashiro who, despite never having done anything wrong, had been abused and taken advantage of their entire lives. Fūshin and the others wanted to help those on the fringes of society in ways that nobody had ever helped them. The Lightning Group attacked murderers, thieves, and other wrong-doers and took everything they had. They then dispersing the plunder to those in need, primarily small settlements like Bamboo Village that were often neglected by their countries.
The Lightning Group became famous within certain circles, attracting new members to their cause and receiving warm receptions from those they helped. They eventually gained the attention of Kirigakure, who hired the Lightning Group to deal with a group of politicians embezzling funds from their constituents. When they confronted the politicians, however, Kiri came to the politicians' defence; the Lightning Group had been hired only to create a reason for Kiri's employment. Most of the Lightning Group died fighting the Kiri-nin, and the handful of survivors tried to find refuge in the villages they'd helped. None would give them shelter, fearful of reprisal by Kirigakure.
Unable to find help and with Kiri still pursuing them, the Lightning Group disbanded and its members went into hiding. All remained angry for how they'd been treated, attacked despite only wishing to do good. Fūshin, Amuda, and (in the anime) Chino decided to seek vengeance against the hidden villages, whose preaching of peace were so often at odds with their covert actions. Karyū decided to take out his frustration on the villages that had refused to give aid to the Lightning Group, and to that end created the Dark Thunder Group.
de:Blitz-Gang
fr:Raikô
it:Gruppo del Fulmine
pl:Grupa Błyskawicy
tr:Yıldırım Grubu
pt-br:Grupo do Relâmpago