Had four instructors over the years (ASEL, ASES, Tail-draggers and gliders)and found them all to be excellent.
Only time I came close to upsetting one was doing FAA ground work @900' AGL. Had done several dummy circuits over fields - you know, warm afternoon, everything going well, starting to doze...... then on circuit 5 or 6 I pulled up too quickly before applying power - the a/c stalled in short order (amazing how quickly it can happen when you're not practicing it). Despite stall warning buzzer and buffeting I still kept the stick too far back. Instructor literally heaved the column forward and we recovered at about 400' AGL.
A quick rebuke followed by stony silence all the way home followed. On balance, not surprising - I'd come pretty close to killing him!
