What is the best Photo App editor on iOS ?

I'm with you for VSCO - it's my daily photo editor on iPhone. Versatile, straightforward, and rock solid.

I think this is the easiest. Very straightforward as @Willie Morris said

I tested a lot of Photoshop alternatives, and I think Pixelmator is the best out there.

I'm amazed not enough people know of this. This app is by google and is extremely well made and has a whole load of features. Best part, completely free!

A must-have for me.

Enhance, tweak, and decorate your photos to perfection with Picture Perfect’s powerful array of tools. Designed by the professionals as an all-in-one photo editor, Picture Perfect lets you apply expertly crafted presets, then adjust details like color, curves, sharpness,auto contrast, auto tone, blur, sharpen, oil paint, sketch, black & white high contrast, sepia and so much more. Whether you’re looking to do a quick edit or produce something more polished for an important project, Picture Perfect’ stunning app will wow and delight you.

Picture Perfect is very easy to use!

Edit exposure, contrast and other light and color adjustments, add effects and crop your photos. It even includes lens correction and, with a Creative Cloud subscription, you can edit selectively, sync photos across devices and edit your photos in raw.