So this is a list that is mainly focusing on the villains that are originally from this series. We're excluding Disney and Final Fantasy villains (Sephiroth is the only villain that I can remember that appears in the KH series) from this list since any villains that aren't originally from the series don't count.

1.Vanitas

2.Ansem

3.Xigbar

4.Xemnas

5.Marluxia

6.Luxord

7.Larxene

8.Demyx

9.Saïx

10.Xaldin