My first instructor (military) used to smack me over the head with a rolled up newspaper every time I made a mistake. As I was very underconfident, this did nothing to improve my performance. He was unwilling to stop even after I told him that I did not like it, but after I started putting the aircraft into unusual attitudes every time he hit me, he eventually relented and we subsequently got on very well. My second instructor was the worst I have ever had - a rude, arrogant, hectoring bully who gave little in the way of instruction and seemed to think that he needed to prove his flying superiority to me at every opportunity. I eventually asked for, and got, an instructor change. My last instructor was really good. He was newly qualified and always made it seem as if he barely knew any more than I did - maybe it was true! - but at least with him my confidence started to improve, as did my flying. The damage done by my second instructor lasted for years and it was a very long time before I started to develop any confidence in my abilities as a pilot. I used him as my role model of how not to be an instructor when I eventually became an instructor myself.
In subsequent years I have found the same to be true of training captains - there are some real monsters out there and a very few really good ones who really are 'training' captains who genuinely try to train and help people.