SPOILER WARNING: This article contains major spoilers for "Rather the Fallen Angel," the latest episode of Supergirl.
Team Supergirl seriously misplaced their trust in Manchester Black. In "Rather the Fallen Angel," the latest episode, Black turned Supergirl over to the Children of Liberty and attacked J'onn J'onzz in his pursuit of vengeance.
Over the course of the episode, Black continually came to Supergirl's aid as she searched for the Children of Liberty's base of operations. Though she objected to his violent methods, she relied on J'onn's word that Black was a good man. She turned up to his apartment to tell him as much, only for Brainiac-5 to tell her he had discovered the Children of Liberty's plan: to denote a device much like a small nuclear bomb.
When Supergirl relayed this information to Black, he insisted they go to the island base alone. He explained that Agent Liberty would see a D.E.O. counterattack a mile away; if they went in alone together, they could surprise the Children of Liberty. Supergirl agreed, not realizing Black had other, nefarious plans.
As it turned out, the island -- once an immigration center for aliens -- had power dampeners. Supergirl brought a device to shut them down, but Black managed to tamper with it before they arrived. When she tossed the device, the power dampeners remained effective, significantly reducing the strength of her abilities. Worse, the Children of Liberty were waiting for them and immediately took Supergirl hostage.
Prior to the events of the episode, Black had struck a deal with the Children of Liberty: they would take him to Agent Liberty if he brought them Supergirl. He delivered his end of the deal, but the hate group did not; they brought him to a man dressed like Agent Liberty, but Ben Lockwood was not present on the island. This fake Agent Liberty revealed they knew Black was Fiona's fiance and they tried to kill him, but Black quickly overpowered them. He killed several Children of Liberty on his way out, destroyed the power detonators to free Supergirl and escaped via boat as Supergirl and Guardian dismantled the bombs.
As Black fled, J'onn tracked him down. The two had an argument, during which time Black revealed all the crimes he committed in the wake of Fiona's death. The images Black let J'onn see left the Martian reeling, leaving him vulnerable to attack. Black used this to slip an empathy enhancer on J'onn, which overwhelmed him long enough for Black to escape.
Created by writer Joe Kelly and artist Doug Mahnke, Manchester Black was introduced in the comics as an irresponsible antihero turned villain. Manchester led a team known as The Elite, dispensing lethal force in the name of justice -- which put them on a collision course with Superman. As such, it isn't surprising to see Supergirl's version of Manchester Black take such violent actions in his quest for revenge.
Airing Sundays at 8 pm ET/PT on The CW, Supergirl stars Melissa Benoist as Kara Danvers, David Harewood as Martian Manhunter, Mehcad Brooks as Jimmy Olsen, and Chyler Leigh as Alex Danvers.