Quote Originally Posted by Jiro View Post
Is it the battles at Fort Condor? I'm trying to think of what else you're forced to do once... Fort Condor has an upper limit though, so perhaps not.
The first fight at Fort Condor is not mandatory, you just just walk by it without ever entering the place once.

I think the answer may be when you go through the forest that requires the Lunar harp, you only have to go through it once when you go through it the first time, but you can go through it many times after that if you so choose to do so.