General Editing
Windows
Fotor
Serif Photo Plus
Pixlr
GIMP + G'MIC (plugin) :star:
PhotoScape
Paint.Net
Polarr
Pixlr-O-Matic
PicMonkey
RawTherapee
BeFunky
PhotoCat
PiZap
iPiccy
DarkTable (also for Linux) :star:
Mac
Fotor
Pixlr
GIMP + G'MIC (plugin) :star:
PhotoScape X
Polarr
Pixlr-O-Matic
PicMonkey
RawTherapee
BeFunky
PhotoCat
PiZap
iPiccy
DarkTable :star:
Android
Adobe Photoshop Express
Adobe Lightroom Mobile
Photo Editor
BeFunky
Snapseed
Polarr
iOS
Adobe Photoshop Express
Adobe Lightroom Mobile (iPad only)
Photo Editor
BeFunky
Snapseed
Noise Reduction
Windows
Helicon Filter
Neat Image
NDNoise
Mac
Neat