From the Emmy-Award winning TV series, Game of Thrones. In the A Song of Ice and Fire novels, Janos Slynt was a commoner, a butcher's son, who joined the City Watch and rose through the ranks first to captain of the Iron Gate and then to become its commander at the death of the former commander, Manly Stokeworth. The City Watch, or "Gold Cloaks", is one of the few institutions in Westeros to permit promotion of non-nobles from the ranks. He is a somewhat humorless man who is arrogant and proud of his achievements. He is bald, stout, and heavily jowled, often described as frog-faced and shaped like a keg.
Janos Slynt was a disgraceful, arrogant and corrupt man who would commit any action given to him by the king or queen, without hesitation, remorse or honor as long as he perceived to get benefit from it.
While he claims to be a loyal and faithful servant of the King and his main priority would be serving him and to defend the city, Janos's true drive appears to be to obtain power through political positions and abuse such power to dominate his command over others by the use of immoral and cruel means, and later defend such actions by stating they were justified in the name of the king or otherwise. Amongst other things he accepts solicited bribes from criminals and other members of the City Watch.
Janos naturally enjoys authoritative positions, having found himself in them his entire life, including Lord Commander of the City Watch, member of the small council, head of House Slynt and an unspecified high-ranking position in the Night's Watch. However, this is more of a compliment to his ability to squirm his way into the favor of other people with high-ranking positions by blind obedience and being outwardly sycophantic rather than his own accommodations.
Janos is not above treachery or hypocrisy at times. He would never have risked his position by doing the honorable thing and helping Eddard Stark remove Joffrey Baratheon from power, instead he betrays Eddard and his men on the spot and defends this to Tyrion by saying he was a traitor who attempted to buy him off, ignoring that he was already bought off by Petyr Baelish in the first place. A common mistake Janos usually makes is believing himself an important or valued necessity, whilst he is usually disregarded altogether. When being exiled to the Night's Watch, he proclaims he has "powerful friends" who would be upset about this but in reality, no one appeared concerned over Janos's exile. He uses this excuse again when about to be executed, unaware that Tywin Lannister was dead and he was making empty threats. Finally, when Jon Snow orders the to take Janos outside so that he can execute him, he stands staunchly as Alliser Thorne seemingly defends him, only to be shocked when Thorne moves aside and lets them have their way with him.
Janos's rise to power has been based almost only on his serving under corrupted people who needed someone willing to do any kind of dirty job for money and power. Unfortunately for him, being too arrogant and stupid to understand how his flattering attitude towards those he perceived as powerful wouldn’t have protected him forever, at some point he has always crossed the line, therefore other powerful people, who instead were able to see beyond his supposed usefulness, got a final confirmation on how far he is from being the valuable person he liked to think himself to be and therefore they got rid of him.
In fact, beneath his confident and defiant exterior, Janos was actually a coward. While other Lord Commanders of the City Watch were either knights or had some knowledge of the battlefield, he possessed none of these traits. He preferred attacking those who couldn't fight back, including Eddard's defenseless soldiers in the Throne Room and Barra. His cowardice was displayed during the Battle of Castle Black where he hid with the women and children and, when finally realizing Jon was serious about executing him, broke down in tears, begging and claiming, "I've always been afraid." He died begging Jon for mercy even though he didn't show any mercy to Ned Stark's men, Barra, or any of Robert's bastard children when he killed them, dying the pathetic and disgraceful person he always was.