B. Dunbar (died November 19, 2018), was a guard at Slabside Maximum Security Prison and one of the guards who let the prisoners out of their cells for Danny Brickwell for his fight club. He was killed by Stanley Dover.
B. Dunbar was a prison guard at Slabside when Oliver Queen was imprisoned and was helping Danny Brickwell, Derek Sampson and Ben Turner with their fight club until Oliver crashed it. Afterwards, he started treating Brick and the others like all the other prisoners instead of treating them like leaders.
B. Dunbar was killed by Stanley Dover who planted evidence to make it look like it was Ben Turner who murdered him.
After Dunbar was killed, Officer Felton, who has replaced Peter Yorke, led a group of guards to Stanley Dover's cell accusing him of the murder for being the last one who saw Dunbar alive, then they dragged him away in isolation while Oliver Queen watched the scene speechless. Oliver then visited him in the isolation cell and asked if he was okay, to which Stanley replied that the guards took turns in beating him up trying to get a confession as they have yet to find the murder weapon.
As Stanley repeatedly stated that he'd never hurt anyone, Oliver asked to tell him how they said Dunbar's murder happened, prompting Stanley to tell him he was killed in the showers and to swear that he wasn't even close to that room when it happened. After Oliver reassured him that he would help him, Stanley told him that he knew that if anyone could prove his innocence, it's Green Arrow.
A few hours later, Oliver found Turner's shiv hidden in the shower room and turning in the weapon, leading to the latter being sent into isolation despite insisting that he was the wrong guy. Oliver later found out that Stanley killed Dunbar and manipulated him into blaming Turner due to planting evidence. Oliver then ended his friendship with Stanley and made amends with Turner, who eventually got released from Slabside on parole. When Stanley escaped from Slabside to target Oliver, his family, and team after killing former corrupt politician Kullens, Oliver incapacitated him. Stanley was later taken into custody by the SCPD and subsequently sent back to Slabside. It is still unknown whether murdering Dunbar was added to his record or not even though Dunbar got justice for his murder.
It is very likely that murdering Dunbar, as well as Stanley's recent crimes, such as the murder of Kullens and two other victims, and the attempted murder of Dinah Drake, Oliver Queen, Felicity Smoak and William Clayton respectively, have increase Stanley's prison sentence from several years to life in prison.
Initially, Dunbar appeared to be a thoughtful guard who had the self-centered Peter Yorke fired when he thought Yorke tried to kill Oliver Queen. Because of the way that Yorke behaved, it was hard for Dunbar to trust him. However, he was revealed to be a selfish individual when he helped Danny Brickwell start a fight club with the rest of the guards. After Oliver broke up the fight club, Dunbar started to treat Brick badly out of regret for aiding him.