Sean Sonus is a villain in the fifth season of Arrow. He is a crime lord in Hub City and a long-time enemy to Tina Boland, whose partner he murdered three years ago. When attempting to recruit Tina, the Green Arrow is forced to come to Hub City to take down Sonus first.
Sonus was a member of Central City's criminal underworld and eventually came under of CCPD detectives Tina Boland and her partner Vincent Sobel. When he found out, he sent his men to capture Tina whom they tortured for over two weeks to find out what the police knew. When Tina refused to cooperate, Sonus sent his men to capture Sobel as well and he had Sobel brought before the captured Tina. Sonus kicked Sobel to the floor and executed him in front of Tina's eyes. However, at the same moment the S.T.A.R. Labs Particle Accelerator exploded, dousing the entire city with energy. The explosion gave Tina a sonic scream which she used to escape. Sonus disappeared around the same time as Tina did.
After the death of her partner, Tina used her newly found powers to become a vigilante. However, she also started hunting down the member of Sonus' gang and followed Sonus through the entire USA, eventually arriving in Hub City where Sonus intended to use the power vacuum created through the death of the city's crime boss Tobias Church to take over. Sonus started a criminal empire in Hub City, selling the drug Slide. He even sold the drug to kids.
New Black Canary
Tina eventually tracks down Sonus in his hideout and takes out all his men. When she confronts Sonus himself, he recognizes her and does not seem too worried, joking about how Tina seems to be far outside her jurisdiction. When Tina claims that she did not come as a cop this night, Sonus reveals that he has become a meta-human as well and uses his powers to impair Tina's sense of coordination by shooting sonic waves at her, causing her to get off balance and fall to the ground. Sonus draws his gun to shoot her but is disarmed by the Green Arrow. Sonus then uses his powers on Oliver as well but Oliver manages to shoot an arrow into his shoulder nonetheless. Distraught, Sonus uses his powers once again to throw Oliver to the floor as well and uses the oppurtunity to escape.
After regaining their sense of balance, Oliver and Wild Dog decide to go after Sonus. Tina informs them that he will be taking a major shipment of Slide, but refuses to cooperate with Oliver and his team and walks off to go after Sonus alone. Oliver later catches up to her and convinces her to let them help her.
At the drug site, Sonus awaits a helicopter delivering his shipment. When Oliver, Wild Dog and Tina storm the roof, Sonus sends his men at them but all of them fall swiftly to the vigilantes. Sonus then attempts to use his powers to stop them but is unsuccessful as Wild Dog has a device nullifying his powers. After all of Sonus' men, including the helicopter, are defeated, Tina confronts Sonus at gunpoint. When Oliver and Wild Dog turn up, Oliver talks to Tina to convince her not to murder Sonus. However, when he asks her what her partner would want her to do, Tina shoots at Sonus multiple times, killing him.