No KB Delay
This plugin fixes a bug which causes entity positions to not be updated on the client immediately after being knocked back. This causes knockback to feel delayed or laggy.
With No KB Delay, entities updated positions are sent the same tick they take knockback. This takes the jittery updates that would result in 1-2 ticks of delay on players, and 1-3 ticks of delay on other entities, and reduces it to 0.
This impacts all players the same. This means that regardless of if you are on high or low ping, this will reduce the delay for when you see entities take knockback by the same amount. This issue even happens on single player, and can be seen in the minecraft bug report MC-297196.

Other Info
You can set the delay to any value less than an entities update interval. While I dont know why you would want this, this would give you delayed, but consistent knockback. For most entities, the update interval is 3, while for players its 2. The command to change this is /setKBDelay, or /skd.
This plugin DOES NOT change any knockback mechanics. Entities will take the same knockback as vanilla. The only difference is when the client updates the entities position.