- "You can't bargain with me. You buy or you die."
- ―Diamondback to Domingo Colon
The Massacre at Colon's Gym was a successful attempt made by Diamondback to eliminate his criminal rivals.
When Diamondback learned that Shades was now assisting Mariah Dillard, he decided to take matters into his own hand, interrupting the meeting that they were having between Dillard, Domingo Colon and several other mobsters based in Harlem. Diamondback explained that he had become offended that the group were not buying Hammer Industries weapons from him anymore, which was now affecting his income and pissed him off, leaving all of the men fearing for their own lives.
Diamondback shot Peter Hong through the head before throwing a knife straight into the eye of Jacques Alef, killing them both instantly. While the group all sat in terror and then awaited their own deaths, Diamondback explained that he had killed Colon's men outside and moved behind Neville Barnwell and shot him through the throat, with the bullet then managing to strike Juan Carlos Castro in the eyeball. Colon called Diamondback crazy for his actions, but he was unfazed, explaining that he had no issue with Colon's cousins elsewhere and therefore he would be keeping him alive for the time being.
Going over to Dillard, Diamondback called her crazy for not reacting to the murders before asking why they should be friends. Dillard suggested they had a mutual enemy in Luke Cage who had allegedly killed her cousin Cottonmouth, telling Diamondback that he should be making a profit on the fact that Cage was now a target, explaining that he should be selling the new Judas Bullets to the New York City Police Department as they needed a weapon which could kill Cage. Diamondback agreed and ordered her to go suggest the idea to the police herself due to her own political position.
Collecting his knife from Alef's eye, Diamondback apologized to Colon for making a mess while he cleaned the knife. When Colon asked why he was being kept alive, Diamondback explained that he would soon be having other mobsters in New York City questioning what had happened, and Diamondback wanted Colon to explain that if they dared challenge him, he would kill them all. Making a final point that he was not a man who could ever be bargained with, Diamondback then left to get a meal at Peter Luger Steak House with Shades following closely behind him as he walked out.
Returning into Harlem's Paradise, Diamondback then watched the performance of The Delfonics until he was interrupted by Shades, who informed him that a video of Luke Cage attacking some police officers had gone viral. When Shades asked what should be done about this, Diamondback told him that it was great news as it meant Cage no longer had anywhere to run and they would soon be able to find and kill him.
Diamondback ordered Mariah Dillard to meet him outside his warehouse located just outside of New York City, insisting that she not be driven by her assistant Alex, explaining that he would have had to kill him and that he would not have come to her as he considered that power should not travel. Dillard however argued that Diamondback had no real power without working with her political influence.
Taking a tour inside the warehouse and showed of his Judas Bullets, explaining that they were made with Chitauri metal, although Dillard was not so impressed as he had failed to kill Luke Cage with them yet. When Dillard questioned who would be able to pay for the bullets, Diamondback explained that they could be broken down into smaller bullets to be sold for mass-production to be used in machine guns which were only slightly less powerful. Diamondback made it clear that he needed all Dillard's political influence to convince the people that Cage had become a threat to their own safety.