Castle 2: Pinnacle is a Manga/Manhwa/Manhua in english language, THRILLER series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

Kim Shin, a special killer who gathered men from all over the country and made the Organization 'Baek-Yi' to destroy the absolute power 'Castle' of the underworld. Through a negotiation he got inside the Castle and started working with the enemy... Will Kim Shin be able to take down the Castle and complete his revenge as he hoped.