On the outside Jack portrays herself to be like rabid uncaged animal lashing out physically and verbally at anyone within arms reach. She is a very complex character though, and easily one of the most well developed in the series. Jack is often just looked at as the punky, tattooed, aggressive and rebellious archetype but if you stick with her she reveals herself to be so much more.
Her need to act out in an aggressive manner, be the most dominant, and the most dangerous character in the group is her way of hiding the real vulnerability and fear of betrayal and abuse. She portrays herself as hating human contact yet definitely yearns it by getting a short quick fix through brief and short sexual encounters.
Her pushing others away through aggressive, violent and sometimes sexual means will eventually give way to the need to belong and feel a part of a community. Through Shepard helping and caring for Jack with no means of an agenda, she slowly learns how what trust means and comes to the eventual realisation that she wants Shepard to be her Alpha and belong to his/her pack.
It is through needing Shepard's guidance and leadership that she eventually realises that she can belong and begin trusting others and more importantly herself by becoming far more than the persona she began with.
Do you think other characters in the Mass Effect universe were just as needing or had as much development as characters?