Kingdoms of Amalur: Re-Reckoning

You unlock the achievement by executing a special attack on an enemy slowed down by a parry. The parry is executed by equipping a shield and pressing at the precise moment the enemy attacks. It is the technique used to unlock the Foiled Again! achievement. A slow motion sequence following the block indicates you successfully performed a timed parry. The special attack is very specific. There are only five special attacks that qualify for the achievement:

In the Might class, Brutal Weaponry is on the far left-hand side of the skill tree. The three Brutal Weaponry IV attacks qualify for the achievement. To unlock them, you must previously have unlocked Brutal Weaponry III and have at least 50 points invested in the Might tree. The three special attacks (with in-game descriptions) are:
Longsword—Riposte: “After a timed Parry, attack with the Longsword to perform a stylish combo.”
Greatsword—Gut Thrust: “After a timed Parry, attack with the Greatsword to impale and launch your enemy.”
Hammer—Crushing Blow: “After a timed Parry, attack with the Hammer to lift and smash your enemy.”

In the Finesse class, Precise Weaponry is on the far left-hand side of the skill tree. The two Precise Weaponry IV attacks qualify for the achievement. To unlock them, you must previously have unlocked Precise Weaponry III and have at least 50 points invested in the Finesse tree. The two special attacks (with in-game descriptions) are:
Daggers—Punishment: “After a timed Parry, attack with the Daggers to perform a series of rapid strikes.”
Faeblades—Savage Wing: “After a timed Parry, attack with the Faeblades to perform a spinning jump attack.”

There are no special attacks in the Sorcery Class that qualify for the achievement.

You must have a shield equipped and the weapon associated with the special attack in either the primary or secondary weapon slot. The special attack is executed by pressing immediately followed by if the weapon is in the primary slot or if the weapon is in the secondary slot. The below video shows the achievement unlocking after the 25th special attack:
Note: You must execute the timed parry successfully denoted by a very short slow motion sequence. To ensure the attack is a special attack and not a regular attack, it must land on the enemy during this slow motion sequence.

Each special attack has a corresponding animation sequence. The animation sequence may be cut short if another action is executed before the animation concludes. Sometimes the special attack animation is barely noticeable because of the rapidity of the follow-on action.

Because it is sometimes difficult to verify the special attack was successfully executed, it is of value to employ the achievement tracker. Make Riposte a favorite so it will show up in the tracker and turn the achievement tracker on. You can then use the tracker to validate your progress towards the achievement. Note the achievement tracker in the bottom right corner of the above video. It advances as the special attack is performed.

Mastery of Arms—Special Case: Note that if you invest 37 points in each skill tree—Might, Finesse, and Sorcery—you unlock the Universalist Destiny. If you equip this destiny, one of its bonuses is Mastery of Arms: Unlocks all weapon mastery abilities. This unlocks all five of the special attacks required for the achievement without the need to invest 50 points in either Might or Finesse. Equip a shield and the weapon to be used for the special attack and you will be able to execute the special attacks by pressing LT followed by the attack button assigned to the weapon associated with the special attack to be used.

Once you have 50 points into the might skill tree you can unlock the riposte ability (Brutal Weaponry IV) for longswords, greatswords, and hammers.(Left hand side, 4 up)

If you have 50 points in the finesse skill tree you can unlock Punishment (Precise Weaponry IV) in it for a "from parry" attack for daggers that works towards this achievement.

To use these abilities do a timed parry (use the shield/block button just before an enemy's attack hits you) and attack directly after it hits. (I just spammed x during the parry)

The full 3 hit combo doesn't have to land, when I got it I only landed the full combo a couple of times.

I popped this achievement in Castle Yolvan (Northwest in the Webwood territory) as there are many giant rats and venomspitters which are easy to parry against because they get into an attack stance, and jump at you making it easier to know when to block.

**Alternatively the Universalist destiny will unlock all weapon mastery abilities including the ones needed for this achievement.
Thanks to 'Dream Fiend' for this.**