"Fanatical devotion" refers to having an extreme and intense level of dedication and loyalty towards something or someone. It suggests a relentless and unquestioning commitment, often bordering on obsession or fanaticism. Full definition
I commented in the past that this card has an almost fanatical devotion among residents in the Pacific Northwest, but I don't think it's about the miles. (travelcodex.com)
Nor does even fanatical devotion to Islam necessarily represent a threat to the everyday lives of Westerners. (relevantmagazine.com)
For years, Colton commanded fanatical devotion in his home neighborhood but had no ability to project power outside his base, and few Brooklyn leaders took him seriously. (observer.com)