SHIRK IS THE GREATEST CORRUPTION
Ibn Tamiyyahرحمه الله said:
'Shirk is the greatest corruption in the earth, rather the corruption in the earth in fact is shirk with Allaah, and differing from His command."
Source: مجموع الفتاوى
Translator: ابو عبد الهادي خليل ديفيس
Abu 'AbdilHaadee Khaleel Davis