How can weakness be negated and strength affirmed for Allah Almighty, even though the name "Al-Rahman" (The Most Merciful) is derived from "Al-Rahmah" (mercy), which might be understood as weakness?

Allah Almighty is unlike anything in His essence or His attributes. Ahl al-Sunnah wal-Jama'ah affirm for Allah what He has affirmed for Himself and what His Messenger has affirmed for Him of names and attributes, without distortion (tahreef), denial (ta'teel), asking 'how' (takyeef), or likening (tamtheel). We affirm for Him the attribute of mercy in a manner befitting His majesty, and we believe that it does not resemble the mercy of creation, for Allah is unlike anything. The attribute of mercy is one of perfection, and we do not concede that weakness is among the meanings of mercy, even if some might think so. For if mercy necessitated weakness in the case of created beings, it does not necessitate it in the case of Allah, for Allah is transcendent above imperfection and need.