Beat this tonight, but after the credits scrolled they said I got the "bad end." My file was at 98%, and I was really only missing one heart upgrade (plus some dimensional fragments).

I helped the critters in the trees, bought the house, fixed the bridge in the bug town... what else is there to do?

You have to get all of the items to get the good end, buy the house and its three upgrades, and do the medicine quest. To get all the items means you need 30 dimensional fragments, but you don't need all 41. Items includes all the hearts, hats, and maps. Once you've got all the stuff, your save file will say 100%, and getting the house and its upgrades will put a + on it. You don't have to pay for the holocade pass, though.

So it was the missing heart that got you, at least. There's a walkthrough here that lists most everything, which should help. (The guide is missing one dimensional fragment in the caves underneath Tomba Island, but that's all.)

Where is that fragment? Could you gove me a hint?

Update: Neevr mind, I got it.