A person's greatest weakness may be defined as: "The starkly missing pieces of his / her life, for which he / she would exchange more than half of their current possessions to obtain".
I just realised the pattern behind everyone's weakness / soft spot. Of course, this includes my own. The 2% I have yet to achieve, which I almost gave up the other 98% for. "Weaknesses" these days, in the age of trade and mutual acquisition, is largely a resultant of the human nature and educational process we have been put through, which tells us at an instinctive level that we have to forgo something to get another.
But truly, since we don't really own anything in the first place, if we could unlearn the mentality of sacrifice, would be end up with no exploitable weaknesses?
Just ranting...