12. Jamie Batista
Angel Batista suddenly has a sister he neglected to mention from season 6 onwards. Replacing Sonya (we never get any clue as to what happened with her) as Harrison's nanny, Jamie proves to be invaluable to Dexter and the maintenance of his double life. Actress Aimee Garcia does a respectable job with the material provided and is especially humorous when butting heads with her older brother.
Never granted a full character arc in the series, Jamie enjoys romantic subplots with Masuka's tech wiz intern Louis and eventually Joey Quinn. Collateral damage in Louis' feud with Dexter, she's crushed to find out Louis records himself with prostitutes when she's not around. The suffering ramps up in season 8 when her pal/Dexter's neighbour, Cassie is murdered and she is dumped by Quinn.
It's all understandably upsetting but Jamie is rarely given the space to be fully fleshed out as a key character. While we sympathise with her plight, it's hard to grow attached in the way viewers would to the original leading characters. This rather lazy approach to development was a general problem throughout the final 3 seasons of the hit series. Jamie was among its many creative casualties.