[annalex]

Saying God's Word is 'useful' is weak enough and then you add a but - as if there is something else MORE POWERFUL than God's Word

You problem is with St. Paul:

πασα γραφη θεοπνευστος και ωφελιμος προς διδασκαλιαν προς ελεγχον προς επανορθωσιν προς παιδειαν την εν δικαιοσυνη

All scripture, inspired of God, is profitable to teach, to reprove, to correct, to instruct in justice (D-R)

(2 Tim 3:16)

I believe, at least one popular translation also has it "useful", but I cannot find it at the present time. My bet would be, it's NIV

No one says the word of God is not powerful. Do you understand the nature of your Bible Alone heresy? I can explain, or perhaps you can do me a favor and read around for my posts to others on exact this topic.

[OLD REGGIE]

All scripture, inspired of God, is profitable to teach, to reprove, to correct, to instruct in justice (D-R)

(2 Tim 3:16)

I believe, at least one popular translation also has it "useful", but I cannot find it at the present time. My bet would be, it's NIV

From your same D-R:

[17] That the man of God may be perfect, furnished to every good work.

Whether "profitable", "useful", or another word it certainly is good enough perfect the man of God.