So for this achievement you need to “Have an attack blocked by an opponent, and then be hit by them within 5 seconds”
This has to be done against an enemy player and not your crew mates. So my tactic for this was to find an island that had a ship already docked off shore. Go ashore and find a enemy pirate. Pull out your sword with
(Might need to press it twice in case you pull out your gun) and just go to town on the pirate with
A normal reaction for most players would be to attempt to block this. Now as soon as you have seen the enemy block one of your swings with their sword, stop moving. Hopefully this invites the other player to attack. As long as they hit you in that 5 second window the achievement will unlock. If for what ever reason they don’t fight back and you end up killing them. Try to leave their boat intact. This will allow them to spawn back on their boat and you can try again
Now I will leave the controls here on how to sword fight but I don’t know how likely you will be able to get into a server to boost with an opponent. If you can great!