According to the World Environmental Performance Index (EPI), Kuwait ranks 126 among countries with the cleanest environment. The #1 rank goes to Switzerland, while the #132 rank (last) goes to Iraq.
As for GCC countries, Kuwait Ranks 5th. Following UAE at #77, Saudi Arabia at #82, Qatar at #100, and Oman at #110 (Bahrain didn’t make it on the list)
You can see Kuwait’s profile with all the categories of the study here