Tony Rodriguez (NYPD Blue)
Rodriguez was given the post of 15th squad commander after the detectives all but rebelled against the unpopular replacement, Lt. Dalto. Lt. Arthur Fancy called in one last favour and had Dalto transferred out - and Rodriguez transferred in.
Rodriguez had previously been a part of the narcotics squad where he had apparently been an enormously successful Undercover officer, to the point where the squad (except for Andy) became excited that their new boss was a "living legend". Andy being Andy was scornful of everything from Tony having facial hair to having opinions, and their differences came largely from the fact that Rodriguez was far more hands on than any of the other leaders the squad had experienced. However, these disputes were generally addressed very quickly and it was clear there was a lot of mutual respect between the two men. Tony's past in Narcotics came back to haunt him when a vengeful dealer he'd put in jail got out and attacked Tony's mom, leading Tony to steamroll other cops and eventually force the criminal to confess to his new crime at gunpoint (which Tony later lied about at a trial).
In Season 10, the Lt. met up with and quickly became romantically involved with his ex-wife, who had left him when she was addicted to drugs. Though she initially claimed to be clean and Tony adamantly ignored reality to defend her, he discovered she was using again and demanded she seek treatment with his help. She ended up fleeing again and being found dead of an overdose. Tony initially demanded a homicide investigation, and angrily accused a man who was also an ex-husband of hers of being involved in her death, before facing the reality of her self-inflicted demise.
Tony had a professional problem with Captain Fraker, an Internal Affairs investigator who hated Tony and made his life miserable, nearly costing him his command in season 9 before Andy shut that down upon learning Fraker had a meritless grudge against Tony and was having an affair with one of his female detectives. After Fraker's dirty dealings were exposed and his career and marriage ruined, he blamed Tony and shot him; only a quick defensive gunshot from Det. Rita Ortiz prevented Fraker from executing Tony. After Fraker was somehow acquitted of attempted murder and Tony was subsequently passed over for a promotion, he decided to retire as squad commander to earn more money in private security. Although he and Det. Ortiz began a sexual relationship around the time he left the squad, it was hinted in season 12 they were no longer dating.
His replacement was Sgt. Eddie Gibson, and later Lt. Thomas Bale.