00 and 04 are guaranteed knockback.
04 pulls the enemy in, 00 pushes the enemy away.
01 is the same as 00, but not guaranteed, knockback resistance has to wear down on the target.
02 is vanilla knockback, where the target is knocked backwards relative to the way it's facing, not the way the attacker is facing, and also not guaranteed.
00, 01 and 04 knockback direction is based on which way the attacker is facing, 02 knockback direction is based on which way the target is facing.