The worst type of turbulence? In my humble opinion - Wake Turbulence. This very under rated effect is rarely examined in detail at PPL level by instructors & pilots alike. Make no mistake, this turbulence will kill you. I have been at the pointy end of an airliner and had 2 wake turbulence events. The first was so severe we had 4 uncommanded rolls of 50°-60° aob which we could do nothing about (6 miles behind an Airbus 330), then we were nearly shaken to pieces. Imagine if this was your average Warrior/Cessna.
Please people, if ATC gives you a "vortex wake, recommended spacing 4 miles" etc then please heed it.
CC