1.从语法角度上说,该句是正确的.
2.You knew me imperfect.
= You knew me (to be) imperfect.
该句是用形容词imperfect做me的宾语补足语.
3.个人觉得：You knew my imperfection.绝对没有You knew me imperfect.好.
后者是更加地道/纯正的说法.
4.如果要讲口语的,可以说成(我把时态改了)：
You know,I have shortcomings/weakness/weak points.