This is incredibly incredibly difficult.
Some things you should practice if you want to attempt this:
Running throw-rolling - This is a straight-forward and easy maneuver to perform.
While running you quickly throw your sword at an opponent when their sword in a low position (otherwise they will auto block your flying sword) and then tap down in the direction you are running to roll and auto pick up their sword.
How to Perform:
Run at your opponent (Optional)
Tap Up and Attack simultaneously (Throws sword)
If running continue to hold forward and tap down (initiates roll and auto grabs dead opponents sword)
Jump Kicking and Downed Execution - This is a somewhat more risky and complex maneuver to perform.
You jump and quickly kick downward at a sharp angle knocking your opponent prone then quickly snapping their neck while they are on the ground.
How to Perform:
While close to opponent Tap Jump and while in the air tap Attack (Performs Divekick)
If your characters body is in close enough proximity to the knocked prone opponent tap attack (Initiates execution)
En Garde Stance - This can be difficult to perform using a gamepad.
En Garde Stance alters how your lunge attack is delivered, it is useful in various situations (narrow tunnels in Mine and the interior of the 'house' at the ends of Forest.)
How to Perform:
Run left and then hold right, while continuing to hold left.
Or run right then hold left, while continuing to hold right.
Dying in any way invalidates the possibility of earning this achievement.
Good luck.