2021 review of 27 studies with almost 8,000 teens and adults found that 1%, on average, express regret. Another study published last year found that 98% of 720 people under the age of 18 who were prescribed puberty blockers went on to continue hormone replacement therapy (and, of that 2%, it may not mean the person isn't trans).
The numbers are also incredibly low — in 2021, it was estimated that less than 5,000 adolescents have taken puberty blockers (which are reversible) in the US over the past five years.
The same report found that less than 300 adolescents in the entire US had top surgery per year. There are around 42 million adolescents in the US total.
A 2015 study on detransitioning further found that most people who did detransition only did so temporarily, and that pressure from a parent was found to be the most common reason given.