10. Tyrus Kitt
We first see Tyrus when Gus has brutally murdered his former chief henchman Victor.
Portrayed by Ray Campbell as a cool and emotionless second in command to the Fring empire during season four, Tyrus spends most of his time keeping his eye on Walt and ensuring he doesn't do anything out of line while Gus tries to groom Jesse.
While he spends his time mainly in the shadows, Tyrus does end up making one of the biggest mistakes in the entire series which leads to the death of his boss.
His failure to spot the bomb planted by Walt on Hector Salamanca's wheelchair was a massive error of judgement that led to Walt finally getting rid of his main source of worry in the show.
Tyrus played a big part in essentially winding Walt up in season four. He watches his every move in the lab, even catching Walt out when he tries to set Tyrus up as stealing meth from Gus. His actions in the lab, coupled with the fact he's the one who captures Walt and takes him out into the desert where Gus threatens Walt's family, essentially make him dispensable in Mr White's eyes.
He's duly gotten rid of by Walt when the explosion in Hector's room does happen.