Vengeful

"The line must be drawn here! This far! No farther! And I will make them pay for what they have done!"

- Captain Jean-Luc Picard's famous line, declaring his revenge on the Borg

"Hello. My name is Inigo Montoya. You killed my father. Prepare to die."

- Inigo Montoya

"(Captain America: This isn't going to change what happened.) I don't care. He killed my mom."

- Tony Stark

Seekers of Vengeance are heroes who commit their actions under the premise of vengeance (also called retribution or revenge), whether it be for a wrong committed against them or their people/race.

History
Similar to a Nemesis, but with a few slight differences: First of all, a Seeker of Vengeance is a specific type of Nemesis, being concerned only with revenge while a Nemesis encompasses all types of motivations; also, a Nemesis is an enemy who is created through the villain's own actions, but a Seeker of Vengeance might already be an enemy to the villains and is seeking revenge for a perceived wrong dealt to them by the bad guy, i.e. Scorpion from Mortal Kombat.

Seekers of Vengeance may also be pursuing revenge against neutral characters or even other anti-villains in Good Vs. Evil scenarios (two examples for this aspect are Ryūko Matoi and Sasuke Uchiha). Another rare example is that the hero/heroine searches for and seeks vengeance against the person who was clearly responsible for their tragedy, until they finally restrain themselves from going too far with their revenge. The best example of this would be Katara from Avatar: The Last Airbender, who seeks venageance toward the man who murdered her mother, though she manages to restrain herself at the last minute.However, sometime the heroes who wanted to seek vengeance against with someone can be failed because get killed by the enemies or they success to do this but almost lose their sense or sanity due unable to control themselves because blinded by their angered, the best example of this Lockon Stratos who get killed by Ali al-Saachez and Louise Halevy who success but she almost lose her sanity because blinded by her angered ( Despite Lockon/Neil get killed, his vengeance was succeeded doing by his twins Brother, Lyle Dylandy ).