Here is the full list of all 16 NENA achievements.
Beat NENA and watch the after credits scene.
This is fine.
Destroy all potted plants in Chapter 1.
Converse with the sentient pebble.
Attempt to kill the sentient pebble at all 3 possible moments.
Possess and reflect the same bullet at least 4 times.
Find the secret room in Chapter 3.
Collect all diamonds in the game.
Beat Chapter 1 in less than 3 minutes.
Beat Chapter 2 in less than 6 minutes.
Beat Chapter 3 in less than 10 minutes.
Unlock all "Speedrunner" achievements.
Beat NENA in one consecutive run without dying.
Possess the car in Chapter 1, but don't attempt to drive it.
Possess a sign.
Kill something using a pebble.