If one has strength, ten years is enough to let an assassin organization rise. Take Li Yan managing 'them', it took much shorter. But it depends on the starting point and opportunities. Take the crows hired by Liu Yuyang, for instance; even after ten years, they are nothing more than aging, weak assassins.
'They' have risen because of the renowned King, Li Yan, as the core leader, and Li Yan gathered the exceptional instructors Yan Ping and Qi Zhongtao, along with the management of Queen Yue Yao. Even so, setting aside the personal achievements of King, 'they' are no more than A-level, which can be considered first-class, but in the face of super first-class S-level organizations, it's still just so-so.
