- "They're not people, they're criminals."
- —Isaac attempting to justify his actions.[src]
At some point Isaac became the apprentice and partner of Ted Grant, becoming a vigilante operating within the Glades. Until he beat a drug dealer to death, after which Ted fired him as his apprentice and partner, and told him to leave and never come back to Starling City. Unbeknownst to Ted, Isaac was abducted soon after by the Culebras who tortured him for months as revenge for the death of the drug dealer he killed. Isaac managed to escape and swore revenge on Ted for abandoning him.
Vengeance on Ted Grant
Isaac began killing criminals and strung up their bodies in Ted's gym and vigilante hideout. Attracting the attention of Oliver Queen, Oliver and Ted began looking for him. Isaac managed to escape and kidnapped both Laurel Lance and Ted and forced them in a car. Laurel managed to call Team Arrow who came to their aid. In the ensuing confrontation he fell out of the car and faced Roy Harper. The two had a hard fight after Isaac got him in a chokehold and told him Oliver just considers him like another weapon in his arsenal, and would give up on him eventually. Roy escaped his hold and managed to knock him out, after which he told him he was not him; in other words, Ted fired him because he brought it on himself.
Isaac was later shown being escorted by two police officers. Carrie Cutter showed up and took out the two cops after which she pointed an arrow at him and killed him. She then dressed his body up with a costume similar to that of the Arrow where it was later found by Quentin Lance and the Arrow.
Before his first appearance, Isaac was impulsive, reckless, but had a sense of justice and honor, and was once a good person, until he crossed the line, when he beat a drugdealer to death, this action of his was what led to him being tortured by the Culebra gang for months as revenge for the death of the drug dealer he killed.
After this, he became angry, vengeful, ruthless, unstable, and a hypocrite, instead of facing the consequences of his actions, he tried to blame Ted Grant, his former mentor and partner, for his actions. He was also not above killing innocent people in his quest for revenge against Ted, he also tried to get into a person's head, like when he said to Roy Harper, "that The Arrow just considers you like another weapon in his arsenal, and would give up on you eventually".
- Expert hand-to-hand combatant: Much like his former mentor Isaac was highly skilled in boxing and unarmed combat; being able to kill multiple armed gangsters by beating them to death with brass knuckles. He was able to nearly fight on par with Roy Harper, but was eventually overpowered by him.
- Skilled marksman/Firearms: Isaac had shown to posses some skills with firearms.
- Stealth: As a former vigilante he had shown the ability to enter and leave an area without being noticed. He was able to infiltrate an area, kill multiple mobsters, capture one and leave without getting detected by Team Arrow. He was also able to sneak up on his former mentor Ted Grant.
- Guns: Isaac was very proficient in using guns.
- Brass Knuckles: Isaac was proficient with brass knuckles.
- Isaac was likely based on Vengeance, a murderous vigilante and an enemy of Green Arrow. Clearly inspired by antics of The Vigilante, Adrian Chase, an otherwise unnamed man used a similar costume (which is also similar to Grant's and Stanzler's vigilante garb in the series) gun, had a specific message to each of the victims ("Vengeance", similar to Stanzler's "Guilty") and was also murdered by Carrie Cutter, Cupid.