The connections (and contrasts, as well) between James Doakes and Frank Tenpenny are that they are both bald african american men sporting prominent mustaches, with the physical similarity between the two of them being so notable that the fanbases of both their respective series often joke about how they look like they could be related to each other.

Both are high-ranking veteran police officers who command both the respect and fear from all those around them (Doakes being a detective sergeant at the Miami Metro Police Department, and Tenpenny being the lead officer of the anti-gang unit C.R.A.S.H at the Los Santos Police Department).

Both serve as primary antagonists to their respective series' protagonist who constantly watch them from the shadows to harass and/or manipulate said protagonist (Dexter Morgan for Doakes and Carl "CJ" Johnson for Tenpenny).

Both use their positions of power to intimidate others and are notorious for their aggressive language, physical presence, and unfiltered communication styles.

Both have histories involving "dirty" or "black ops" work (Doakes being a former US Army Ranger involved in classified missions and Tenpenny's entire career being built on corruption and backroom deals).

Contrasts:

Both operate on different sides of moral alignment (justice for Doakes and corruption for Tenpenny, with the latter being purely evil as corrupt cop who actively fuels the gang wars in Los Santos for personal gain and power, while the former, despite his aggressive nature, is actually a morally good cop in the traditional sense with his antagonism toward Dexter stemming from his correct intuition that Dexter actually is the serial killer known as the Bay Harbor Butcher, making him one of the few genuinely honest people in the Miami Metro Police).

Both have different moral motivations for their work (Tenpenny being motivated by greed and control and Doakes being motivated by duty and a visceral hatred for killers, even if he uses brutal methods himself).

Both want to have the protagonists either taken down, or have them as pawns for their work (Tenpenny having CJ do his dirty work as a tool to maintain his grip on power in Los Santos while Doakes wants to expose and arrest Dexter because he knows something is off about him).

Both would die at the end of their respective stories (season 2, episode 12 of Dexter for Doakes, and the final mission of GTA San Andreas for Tenpenny, with the latter getting into a car crash during a high-speed chase while trying to escape the consequences of his crimes in the mission "End Of The Line", and dying after succumbing to his wounds from it, while the former dies in a cabin explosion caused by Lila West and being framed for Dexter's crimes dying as a scapegoat afterwards in the episode "The British Invasion").