Ken has very high health and attack power along with an Omni Strike and a 100% chance to Knockback all Cat Units, although along with his multi-hit, this can make some of his attacks miss due to both factors.
Turn the animation on and off using the switch in the upper left. Clicking the viewer background enables scrolling and zooming with the mouse if on desktop. Note that browser zoom may cause issues with scrolling and zooming. A list of available backgrounds can be found here. For more info on usage, see here.