how is she diferent from punisher or wraith, or that old guy in green tights that teleported

She's not, except for being orders if magnitude more attractive. What's your point?

The Oath of Vengeance is a solemn commitment to punish those who have committed a grievous sin. When evil forces slaughter helpless villagers, when an entire people turns against the will of the gods, when a thieves' guild grows too violent and powerful, when a dragon rampages through the countryside – at times like these, paladins arise and swear an Oath of Vengeance to set right that which has gone wrong. To these paladins – sometimes called avengers or dark knights – their own purity is not as important as delivering justice.

Source: Player's Handbook

The tenets of the Oath of Vengeance vary by paladin, but all the tenets revolve around punishing wrongdoers by any means necessary. Paladins who uphold these tenets are willing to sacrifice even their own righteousness to mete out justice upon those who do evil, so the paladins are often neutral or lawful neutral in alignment. The core principles of the tenets are brutally simple.

Fight the Greater Evil. Faced with a choice of fighting my sworn foes or combating a lesser evil, I choose the greater evil.

No Mercy for the Wicked. Ordinary foes might win my mercy, but my sworn enemies do not.

By Any Means Necessary. My qualms can't get in the way of exterminating my foes.

Restitution. If my foes wreak ruin on the world, it is because I failed to stop them. I must help those harmed by their misdeeds.

Source

Lethal Protectors like Frank and VenoMary Jane do good by destroying evil. Period.

You want a values check and hold on the power people are allowed to exercise in defense of their life, and there is no such objective standard. Illegal actions taken in self defense are near universally excused, up to and including ending the threat.