In my experience, Japan takes first place for Clear Air Turbulence, and the New England Tableland in Australia for Thunderstorms. Like so many others here, have had many 'bad' trips across the Bay of Bengal, but never a terrible one. The damned B of B even insists on giving it's share of clear Air Turbulence in non stormy days (rare).
It's all a bit subjective about where you've been.
O.S.