Frank Delano was the leader of a crew of corrupt former police officers and a significant enemy to Five-0. He served as a primary antagonist in the later episodes of Season 2 and the premier episode of Season 3.
The operation was so secretive that Kono's colleagues, Lieutenant Commander Steve McGarrett (2010), Detective Sergeant Danny Williams (2010), Agent Lori Weston and Kono's cousin, Detective Lieutenant Chin Ho Kelly (2010) were unaware of what was really going on and even began believing that Kono had gone corrupt although Fryer and Kono later told the team the truth concerning the undercover operation.
Delano was eventually arrested and jailed although in the Season 2 finale episode, Ua Hala (episode), he blackmailed Chin into freeing him from prison and later forced him to choose between Kono and his wife, Dr. Malia Waincroft.
Chin chose Malia and headed home, only to discover that she had been shot. Prior to that, Chin also contacted Kono's boyfriend, Adam Noshimuri who saved Kono from death but tragically, Malia succumbed to her wounds, leaving Chin devastated and hellbent on avenging Malia's passing.
Luckily, though, Hawaii Five-0 caught word and were on the getaway vehicle within minutes with many members of the crew dying in the gunfight that erupted between the two teams.
Delano later fled and attempted to discover, only to be confronted by Chin who shot Delano dead in cold-blood with his shotgun, avenging Malia.
Unfortunately, it was later revealed that Delano had a brother named Paul who kidnapped Chin and put him in prison in the Season 3 episode, Olelo Ho'Opa'I Make (episode) although again, thanks to Steve, Danny and Kono, Chin was saved while Paul was arrested.