Black Noir has been known to speak only once in the comics, when he whispered 'Good Soldier'. This adds to the rumours that he is the "Batman" of the Seven, as 'Good Soldier' is a term usually applied to Robin by Batman. Few other details are known about Black Noir: he is a caucasian male (see the Boys release with the "Rite of Passage" where the newly appointed member of the seven undergoes this rite, we see his posterior in one particularly explicit panel). In Herogasm, Jack said Noir and the Homelander "go way back" (a reference to World Finest).
He is described to have come from the darkest city, and is one of the major members from the Seven. He has several enemies, such as Coagula, Sexface (real alias not confirmed) and a naked girl (spoof of Poison Ivy) who all appear during Herogasm when he raped/fingered Hughie in a sewer. He showed no reaction when Starlight had oral sex with him and does not speak, highlighting his mysterious nature. Very few people are aware of his identity. Noir was stopped by Maeve from forcing Starlight to wear her new, more revealing outfit. His rape of Hughie and forcing Starlight to wear a sexual costume shows his depravity.
When he finally confronts Butcher and the Homelander at the Oval office, it is revealed that he is an identical clone of the Homelander, and MM reveals that Vought-American created Black Noir with refined Compound-V as a contingency plan, in order to ensure that the Homelander never oversteps his bounds, and to kill him if he does. But the mission, coupled with being forced to reside and interact with his target drove him insane, causing him to commit various atrocities in the Homelander's costume, such as cannibalising children, murdering women and raping Becky (Butcher's wife). He sent photos of these to the Boys to incriminate the Homelander, and to give VA a reason to finally order his death. After this revelation, he is assaulted by an enraged Homelander in the Oval Office. However, he easily kills the Homelander, but sustains severe body damage. Walking outside, he is showered with gunfire, and is ultimately put down thanks to Butcher cracking his skull open with a crowbar.
As he is a clone of the Homelander, it can be assumed that he has all of his powers and abilities as well, including super strength (enough to "bench a dozen Mack trucks"), speed, flight, near-invulnerability, heat vision, and enhanced vocal cords.
In Other Media
Black Noir appears in the series, portrayed by Nathan Mitchell. The evidence of his superpowers is left in question during Season 1. In Season 2, we witness Black Noir using considerable super-strength, super-speed, enhanced agility, as well as considerable durability (he survives gunfire, and explosions with no ill effects). During his interaction with a communication security analyst at The Seven's HQ, he only communicates with written notes; it is unclear if he is actually mute, or is simply choosing not to speak. It is also revealed that he his one chronic weakness: An allergy to nuts - Queen Maeve force-feeds him an Almond Joy to allow Butcher and Hughie's escape certain death at Black Noir's hands.