For me its either LoZ or MM.
In LoZ some of the later levels are tough.
Particularly LoZ's second quest.
All the levels are in different places.
Heart containers,weapons, all in different places.
Some you will find by pure luck.
And when you get by wizzrobes and darknuts they take so much life from you.
In level nine the last level,there are just tons of them in every room.
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MM is also very hard.
Especially if you want to find everything.
I find the eart pieces to hard to first find,then complete what you need to do to get them.
So many things take 3 days.
One in particular involving Anju and Kafei.
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I like the facy so many things are spread over 3 days.
Its takes a while to do but so things should.
They should be a challenge.
Another thing that is hard is getting all the fairies from each of the 4 levels.
The fairies in the firstis easy but i find getting the fairies in the other levels impossible.