Grand Fisher was well known and caused trouble for fifty years. He evaded every Shinigami who came after him. I was wondering why wouldn't they send a higher level Shinigami? Ikaku is a third seat and was able to defeat an Arancar who had been an Adjuchas. Yumichika is a fifth seat, it was never confirmed what his opponent had been before becoming an Arancar but it is likely he was an Adjuchas.
Wasn't GF just a normal Hollow in his debut?
If a normal Hollow was causing so much trouble for 50 years could they not have sent a seated officer to get him? I can't really see him standing a much of a chance against many of the high level Shinigami.