The phrase "the one" refers to God. This could be reworded. Alternate translation: "Fear God who, after ... has authority" or "Fear God, because after ... he has authority" (See: [[rc://en/ta/man/jit/figs-explicit]])
This is a general statement about God's authority to judge people. It does not mean this will happen to the disciples. Alternate translation: "has authority to throw people into hell"