Why Was the Bowery King Punished?

After John replies yes, Bowery King reveals that he is waging a war against The High Table for unfairly punishing him and killing his men, revealing that he lied to them about being loyal and stepping down from his position and that he only took the punishment because he was forced to do so.

What did John Wick do to the Bowery King?

Wick cut him two times and gave him a choice to keep pressure on his cut and live or the try to shot him and then bleed ou and die. After that the Bowery King never let anyone else sneak up on him again and went from a pawn to a king.

Why did John Wick kill a member of the High Table?

Santino, craving the power for himself, orders John Wick to kill Gianna as per conditions of fulfilling the marker he made with John. After Gianna's death, Santino immediately took her place within the High Table and ordered his right-hand woman Ares and many of his men to kill John to avenge his sister.