Ideally, some form of moderately safe spacing. Lack of options at close range means people rolling behind you and hitting the shield button is a pretty easy strat to trump almost any offensive response he has, but Ganon's biggest issue, by my estimation, is his inability to deal with safe playstyles. Not just defensive, but safe.
I play a guy pretty regularly who uses Robin and Roy. He refuses to ever commit to anything, and 100% of the time waits for me to come to him, in which case, Ganon's only recourse is hard reads. Even Ganon's "safer" spacing tools like DTilt can still be pretty unsafe.
Ganon's got a few dirty secrets which, if figured out, make life pretty rough (not approaching, etc.). Thankfully his massive power puts an asterisk on pretty much every weakness he has, but all the same.