There are multiple accounts that describe severe pain and the New Zealand government has paid out compensation for the torture that it was. What was being done here was most definitely intended to be painful torture, so maybe isn’t a fair comparison with clinical ECT for actual treatment?

‘Bryon Nichol spent six months in the Lake Alice unit at the age of 12. He said he received electroconvulsive therapy (ECT) many times, which was always unmodified, and without a muscle relaxing anaesthetic. "The nurses would come down and drag me upstairs. I was often so petrified that I soiled myself. They would put a mouthguard in my mouth and held me down while Dr Leeks gave me ECT. The ECT would give me vicious pains in my head and make me feel dizzy and as it continued the pain got worse. My arms and legs flailed about. It was absolute agony."’

And another:

‘Rangi Wickcliffe, 59, is another survivor of the Lake Alice unit. He was 10 when he was first given electric shock treatment. Dr Selwyn Leeks turned the machine on, the pain that you feel from the electricity surging through your head is indescribable. The scream that comes out of your mouth is also indescribable. "The terror was so intense that you lost all bowel movement." He said it felt like his bones would break.’

https://www.rnz.co.nz/news/national/444800/abuse-in-care-inq...

https://www.rnz.co.nz/news/national/444800/abuse-in-care-inq...