righteous
adj.adj. doing what is morally right or fair. If you use it as slang, it means something is excellent or very impressive.
adj. morally upright or justifiable; acting in accordance with divine or moral law. In informal registers, it functions as an intensifier meaning excellent or genuine.
He felt a righteous anger after seeing the unfair treatment.
The activist spent her entire life fighting for a righteous cause that many others had ignored.
While the politician claimed his motives were entirely righteous, the public remained skeptical of his sudden shift in policy just weeks before the general election.
From earlier rightuous, rightwose, rightwos, rightwise, from Middle English rightwise, rightwis, from Old English rihtwīs (“righteous, just”), corresponding to right + -wise (with assimilation of second element to -ous), or to right + wise (“way, manner”). Cognate with Scots richtwis (“righteous”), Old High German rehtwīsic (“righteous, just”), Icelandic réttvíss (“righteous, just”). Compare also thefteous, mighteous.
Typically precedes the noun it modifies; often used to describe abstract concepts like 'anger', 'indignation', or 'cause'.