UK: Radio 4 still puts out at least 400KW am on 198KHz for the time being, but will be phased out in the next decade or so. There is something slightly magic about pumping that much power into an impedance that is basically the air...
Deutschlandfunk also used to operate two 500kW (250kW at night) transmission sites until the end of 2014.
They were shutdown as a cost-saving measure (one of the two sites was even upgraded to more modern transmitters just ~5 years before the end).
https://en.wikipedia.org/wiki/Droitwich_Transmitting_Station
http://www.bbceng.info/Operations/transmitter_ops/Reminiscen...
Edit: typically I can't find a definitive figure for the power output...