I would argue that babies and toddlers wouldn't be held accountable for their bad choices, even though they could foreseeably be life changing for the worst, if they stuck their hand in a blender for example. Although you could argue that in this case a parent/carer should not leave a young child near a dangerous object.

Most people would agree that a person that is fully accountable when they are considered an adult, we usually apply the arbitrary age of 18, although I do find it strange that a person that is 17 years, 364 days, 23 hours, 59 minutes and 59 seconds old is a child and one second later they're magically an adult.

There is definitely a grey area in the early teens or possibly even younger where you can definitely make a decision that ruins your life. An example that comes to mind is when two ten year old boys stole a toddler, then tortured, sexually assaulted and murdered him. They were judged as having the ability to act with criminal intent, found guilty and sentenced to prison.

https://en.wikipedia.org/wiki/Murder_of_James_Bulger?wprov=sfla1