Arcana Heart 3

For this achievement you have to land Fiona's Extend Force Critical Heart in a match against the CPU or 2nd player (2nd player recommended). Training does not unlock this achievement. In total, you have to do a combo with three inputs (plus Extend Force activation). The most crucial part is the timing of the third input.

Select Simple mode. Your default arcana is Metal. Press 4C to charge your super meter until you have 3 bars (this is a Metal arcana ability). On the Xbox controller this would be backwards plus B button.

Now stand close to your opponent, activate Extend Force with ABC (Xbox: LT button), press BC (Xbox: Y+B button) to grab and B (Xbox: Y button) to launch in the air. You can simply mash the second input until you see Fiona rise with angel wings. The timing of the third input BC (Xbox: Y+B button) has to be quite accurate. You have to press shortly after her wings fully disappear. You will notice when you have done it wrong, because the move will do almost no damage. There is a picture of Fiona's eyes in the background behind the character if your timing is almost right (or exactly right). No eyes means your timing is not very good. No sword swing at all means the timing is pretty bad. You should focus on the disappearance of the wings.

By the way, the final move (called Sacred Slayer) does count towards the "Sacrecent" achievement (= perform 100 moves with the word "sacred"), even if your timing is not right.

Select Fiona on simple mode in char select once in match activate Force Gauge with LT, then press Y,B Together to start Critical Heart. Follow up =>Y then press Y,B Together .
The last action is the sword "bang" to the opponent but not slide to, take a few tries and it should pop.
Also similar to Nazuna - Engauge! achievement, Critical Heart won't kill the opponent unless you finish the follow up.

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