IAH my personal best in the US.
SE Asia: Changi for busy airports is good.
Bad: Anything in India; sorry.
Worst: Domestic Terminal at Manila (not the PAL one which ain't bad)
Worst in Europe: Gotta be Gatwick on a Bank Holdiday closely followed by Malpensa!
Personal favourite: DVO (Davao International). Near my home, pleasant staff and gets me where I want to go. Totally under utilised.