Atk Debuff caps at 70 %.
List with 6* Debuff Girls (don't know if it's complete.):
http://flowerknight.wikia.com/wiki/D...(Bride_of_Fos)
http://flowerknight.wikia.com/wiki/R...Shrine_Maiden)
http://flowerknight.wikia.com/wiki/E...rum_(Swimsuit)
http://flowerknight.wikia.com/wiki/Acacia
http://flowerknight.wikia.com/wiki/Horse_Chestnut
http://flowerknight.wikia.com/wiki/Apple_(Tanabata)
http://flowerknight.wikia.com/wiki/Mistletoe
http://flowerknight.wikia.com/wiki/Cherry
http://flowerknight.wikia.com/wiki/Lotus
http://flowerknight.wikia.com/wiki/Ivy_(New_Year)
http://flowerknight.wikia.com/wiki/Golden_Lace
http://flowerknight.wikia.com/wiki/Snow_Drop
I will give you an example for a Debuff Team with Epidendrum:
http://flowerknight.wikia.com/wiki/E...rum_(Swimsuit)
http://flowerknight.wikia.com/wiki/Horse_Chestnut
http://flowerknight.wikia.com/wiki/Apple_(Tanabata)
http://flowerknight.wikia.com/wiki/Snow_Drop
http://flowerknight.wikia.com/wiki/Easter_Cactus
With this Team you have 75 % Debuff (caps at 70%), x1,6 Skill Act, all Damage Types (Weakness Damage from Epidendrum and Horse Chestnut), Counter (Apple) and Revive from Phoenix Chan.
There are many more options: Kerria Debuff Squad for example.
Here is a list of 5* Debuff Girls i know:
http://flowerknight.wikia.com/wiki/Dahlia
http://flowerknight.wikia.com/wiki/Cherry_Sage
http://flowerknight.wikia.com/wiki/Dragon_Fruit
http://flowerknight.wikia.com/wiki/Green_Bell
http://flowerknight.wikia.com/wiki/Apricot_(Christmas)
If you don't want to spend money or rely on luck to get a full 6* Debuff Squad try to get those 5* Girls. You can hit the 70% mark relatively easy.
I hope this will help you