If you’re looking for a photo editor that’s in the same professional echelon as Photoshop, Affinity is one of your best (if not the best) options. While you’ll have to pay up, that money will secure you a photo editor/creator capable of smoothly handling professional workloads (support for photos over 100 megapixels) and a feature-rich editing suite that’s versatile enough for pretty much any creative project. It’s also a one-time purchase, so no forever bills here.
If you’re looking for a quick and easy way to edit or create photos from scratch, Pixlr will most likely have everything you need (and potentially more) in a neat, browser-based suite. There’s an automated cutout tool, built-in stock photos for creating images from scratch, layering, a simple UI, and it can open Photoshop files if needed.
If you’re looking for something more focused on illustration rather than photo editing, then Krita is an ideal and budget-friendly (read: free with a suggested donation) choice. Krita is not only free, but open-source and loaded with 100 built-in brushes, vector tools, and features like brush stabilizers to help keep your drawing smooth and steady. For proof of Krita’s capabilities, just check out some of the creations featured on its site...
Another entry among the paid options is Pixelmator, which should be a consideration for anyone in the Mac OS and iOS ecosystem. Pixelmator offers a $5 iOS app for light photo editing that comes with features like color correction, blur, cloning, and fine color and brightness adjustment as well as a Pro version for Mac OS for more professional editing.
If you’re using Windows (sorry Apple folks), Corel Paintshop Pro is a versatile alternative to Photoshop that can be used for photo editing, drawing, and and graphic design. Corel has pretty much all of the standard features you’d want in a Photoshop alternative, including a robust selection of brushes and AI tools for photo editing, but shines in its ability to customize the the UI to fit your particular workflow or skill level.
A feature called Workspaces, for example, allows users to choose between an everything-and-the-kitchen-sink interface and an “Essentials” interface with only the tools you need — both of which can be customized to your liking. This ability to tailor UI makes PaintShop a good choice for beginners and experts alike.