The answer here, to the question "Who really destroyed the Luftwaffe" would be "They all did"...
It was the determination and multi-front air war that ground the Luftwaffe into the ground...literally.
People will (and are) argue that one air force did all this, and that air force did that, but it was the fact that the German leadership expanded thier war into a multi-front disaster that thier resources and manpower could not sustain.
While the Luftwaffe and thier allies put up a tremendous fight, the sheer weight of numbers of the RAF, USAAF and Soviets along with thier allies combined, finished the Germans off.
Yes, the USAAF's combined bomber/fighter offensive hurt Germany, but the early bleeding by the determined RAF dealt Germany a blow that was felt for the rest of the war. The meat grinder of the Ost Front was a slow hemmorage to the Luftwaffe, committing vast resources of the German war machine.
So in the end, it wasn't any single Allied airforce that won the war, it was a concerted effort, no matter how small the role, that took down the Luftwaffe...