User blog comment:IamJakuhoRaikoben/Chapter 501: Mari and Randi, Review./@comment-27281341-20160912202210

I am pretty sure that Brandish's shrinking ability can be countered by anyone who has much more magic power than hers. It's implied ny her reaction when she tried t use it to Neinhart. So, it would probably be impossible for her to use it against Acnologia. Dragons might as well be immune to her magic.

Now against DiMaria, well, any time mage more skilled than her could nullify her time stop. And maybe, opponents with higher magic power than hers could move freely even inside her Age Seal. So again August, Zeref, Irene, the Dragons and Acnologia can probably counter her just by their raw power. Since it has been stated that even with Fairy Heart, only Zeref has the potential to beat Acnologia, it is a given that he could in some way counter her magic.