Wściekła pięść and other 65,000 icons from Icons8 icon pack follow the visual guidelines of the operating systems: Windows, iOS, Android KitKat, and Material. PNG format is free up to 100x100 px. Icons are availble for download in PNG and vector (SVG, PDF, EPS, and more).
This icon shows an outline of a fist up to the wrist. All of the fingers and thumbs are folded in to indicate that it's closed. There are lines on either side of the hand to indicate that it's shaking out of anger.