This list is entirely based on attractiveness, character and personality and not judged by strength. Think of it as an One Piece beauty pageant.
WAIFU Category
1. BLACK MARIA
2. NICO ROBIN
3. BOA HANCOCK
4. BACCARAT
5. VINSMOKE REIJU
GODDESS Category
6. NAMI
7. SHIRAHOSHI
8. YAMATO
9. WHITEY BAY
10. CHARLOTTE LINLIN (Rocks)
11. HINA
HOT Category
12. NEFERTARI VIVI
13. JEWELRY BONNEY
14. NOJIKO
15. CHARLOTTE GALETTE
16. KALIFA
17. ULTI
18. BELO BETTY
19. BABY 5
PRETTY Category
20. KOZUKI HIYORI/KOMURASAKI
21. TASHIGI
22. DOMINO
23. VIOLA
24. CARROT
25. REBECCA
26. GERD
27. MONET
28. PERONA
29. CHARLOTTE PUDDING
30. CHO
If you're not familiar with some of the characters, I've tagged them below.