Apps with 'Symmetry brush' feature
GIMP is a free program for such photo retouching, image composition and image authoring. Essentially it's the closest thing to Photoshop you can get for free.
Professional, open-source raster graphics editor with advanced digital painting and sketching tools and workflow features.
Animation Desk is a perfect tool for animating, storyboarding, and sketching. It’s an app Loved by professional and amateur animators, Youtubers, and many art lovers.
Generate tags for Youtube Videos. Works as a browser extension.