Since Joshua's Guide don't actually cover combo locations, I decided to make my own guide. You need all of them to 100% Complete the game. Also, successfully done, each of the three last combos reward you with extra lives, isn't that nice?

You can't miss it, it's on your path.

You can find the totem under those fragile platforms.

Pretty much at the beginning of the third level.

You need to reach the mud area with the dead fish spirit. Jump on it to reveal a secret area and reach the ladder.

During the last part of this fifth level, you are forced to slide on rapids and to jump on monsters. Watch out for a secret ladder and jump with the right timing.

Near the end of the level. Jump on the spider heads and reach that secret area to the left.

Toward the end, use the mushrooms to reach a secret ladder.

Once you come across this particular checkpoint, get down very carefully.

Pretty easy to miss. Near the beginning, don't be afraid to jump down into the gap.

I hope you have found this guide useful, if so please consider rating this guide!
Also feel free to check my other achievement/walkthrough guides here.
Thank you!