Canva Photo Editor (FREE) – https://www.canva.com/photo-editor/
The Canva Photo Editor is hands-down the easiest online photo editor to use. If you can drag and drop an image into your web browser, you can use this editor. There are only six operations that you can make: filter, adjust, crop, resize, rotate and flip. Canva Photo Editor is great when you just need to resize and save an image.