The Essence
While Al-Qaadir is the Able, Al-Muqtadir is the One who actually manifests that power into reality. He determines the exact measure of everything and enforces His will flawlessly upon all creation.
In the Quran
فِي مَقْعَدِ صِدْقٍ عِنْدَ مَلِيكٍ مُقْتَدِرٍ
"In a seat of honor near a Sovereign, Perfect in Ability (Muqtadir). (Surah Al-Qamar 54:55)"
In Your Duas
يَا مُقْتَدِرُ أَقْدِرْنِي عَلَى فِعْلِ الْخَيْرَاتِ
"O Muqtadir, empower me and grant me the ability to perform good deeds."
— General Supplication (Quran 7:180)