In another thread there is a debate over how unrealistic knockback is. Setting aside the notion that knockback is as realistic as someone hoisting a full-sized car and then throwing it any distance at all, I can see where some folks don't like knockback. Personally, I've only used Knockback in superhero campaigns. It just doesn't belong anywhere else (except in a tooniverse, where it should be even more unrealistic).
In my own opinion (and in my own campaigns) attacks which do not impart kinetic energy to the target (lasers, heat rays, etc.) did not do knockback. Killing attacks that rely on making small holes in the target (arrows, cmall-caliber bullets, stillettos, piercing swords: epee, foil, rapier for example) would do less KB than a normal attack.
If you agree that knockback needs "fixing" how would you do it? Would it take into consideration that heavy objects (or heroes) striking lighter objects might impart more motion than the reverse? Tell me. How would you reconstruct knockback?