Knockback is the strength of the launching power of attacks. Every attack has its own degree of base knockback. Just like damage, if there’s a sweet spot, it improves the knockback, maybe adding a special hit effect, like a meteor smash.
Generally, high-damage attacks dish out more knockback. It’s high-knockback power that makes moves credible knockout threats, once enemy damage builds up to medium and beyond. Yet you’ll find the occasional low-damage attack with respectable knockback, or a move with reliable damage that nevertheless lacks KO potential.
Aside from varying attack to attack, knockback also gradually increases as foes take damage. Thanks to the rage buff when badly hurt, knockback for a high-damage fighter is increased both for and against them.
Some strong moves might be great for knockdown setups or home-run swings to score a knockout, but their hit effects don’t reveal themselves at lower-damage percentages, where they seem like regular pokes. Their strengths become apparent at medium- and high-damage percentages, where targets aren’t as sturdy on their feet. When strong moves with lots of knockback blast someone backward, being closer to the blast zone behind them makes a difference.