And in my eyes, that’s the missing link. Respect of the other; of his/her need for kind gestures no matter of how tinny. And respect for the other so that we put all effort to communicate properly with him/her no matter how trivial the matter is.
If by "major" you mean most important to society... then Aretha's anthem may be the one. If you mean what is important to most individuals: the strongest pull is the need to be right. Right?
@OP: Totally agreed!
I think the major need is to connect. We connect in many ways, and almost all are important. One of which is to romantically connect to someone.