Bayonetta

The Moon of Mahaa-Kalaa is an awesome but expensive accessory from Rodin's Shop. It's well worth it though - as far as I'm concerned, it's an essential accessory that should never be unequipped!
It has 2 functions - a deflection and a counter. Both are performed by pushing the left stick towards the attacking enemy as they launch an attack. The only difference is timing.
The deflection is easy and can be achieved by mashing the left stick towards enemies in anticipation of attacks. It bounces projectiles back, stuns enemies after melee attacks and refills a single magic orb.

The counter, which you want for this achievement, requires much tighter timing.
Notice how a red rose appears on Bayonetta when you get hit. You need to push the stick the very moment this happens. As for a lot of the achievements, I recommend the prologue. Kill all but one of the enemies from the first wave - this will allow you to concentrate on learning its timing without being blindsided by others. Just keep trying and really try to notice audio and visual cues to help with your timing.
If you're having trouble, try equipping the Gaze of Despair as well. It angers enemies and makes them stronger, but also faster. I find it much easier to counter fast attacks as there's less time to act too early and accidentally perform a deflection instead.

One more tip! Counters activate an extended period of witch time, refills 3 magic orbs, refills a little bit of health and unleashes a powerful wicked weave attack. This attack might kill your opponent before you've performed 3 counters so you want to cancel it! Just after countering and activating witch time, dodge. This will cancel the attack and leave your opponent unharmed, allowing you wait for their next attack.