I am not sure what you mean by ''a strong and weak ego''. I presume you mean the amount of self importance of the conscious subject.
I believe that the ego is never done with evolving. The degree of regard for our own importance in relation to reality changes with every experience we have.
I have been thinking about what sort of experiences would affect the ego but that might be something very subjective but my gut feeling tells me some things work the same for us all. Experiences where other beings acknowledge and respect you will enforce and support the ego,things like friendship, love, raising a child or even something as small as a smile. I believe that deep inside every human wants to be acknowledged for what he is by his peers. if that is lacking then the ego will suffer.
qwertz wrote:By "boundaries crossed" you mean any form of treatment that shows a lack of respect?
What about more standard types of parenting (by standard I mean that don't include something immediately remarkable such as abuse)? What kind of parents do you think produce a strong and what kind produce a weak ego?
A very strong ego is not necessarily a good trait either since such a person would be very rigid and would have a difficult time handling with hardship because of an inflated feeling of pride and self importance. While a person with a very low ego would suffer from self imposed hardship from a lack of self worth. I think that the parents that accept, support and love the child for what it is will produce a human with a healthy ego.