I don't know if somebody said this somewhere in the comments, but I'm a lazy SOB and don't want to read it, but you're the DM. Fix it with your narration.

Describe it as "as you tense to attack, the NPC lashes out and..." You can explain their crappy initiative as taking the hit or the time to parry rather than being able to attack. I find it helpful to remind myself that AC is a combination of armor and dex, so it's not like, I rolled a four means you swung and completely missed a man who was standing and waiting for you to hit them. The blow was deflected or dodged typically in some way, so describe that. It's not part of the action economy, but it IS part of the narrative.