Great Aether

Great Aether (大天空) is Ike's Final Smash. It was described by the DOJO!! as a more powerful version of his Aether. Ike becomes invincible and swings his sword in front of him and anybody who he hits is sent upward. He then leaps into the air, slashes the character(s) seven times with his sword aflame, kicks them twice, slashes them four more times, and knocks them downward with a powerful finishing blow, similar to Link's Triforce Slash. Upon impact with the ground, a large explosion knocks away the trapped character(s) and any character that happens to be too close.

Attack Overview
The attack does about 64%-74% damage (52%-62% from the attack, 12% in the explosion), and is one of the most damaging Final Smashes in the game. If the opponent is very close to Ike when he uses it, the initial hit will deal 15% damage, but if they're further away from him it deals only 5% damage. Because the knockback from the explosion is vertical, opponents may not be KO'd immediately due to the high blast lines on some stages. In most cases, however, the move does provide significant knock back to launch enemies off the screen. Multiple enemies can be picked up in this attack and, although Ike is invincible during this move, Ike's victims can be attacked by other players along the way down. The move elevates Ike to the highest point on the stage and always takes place in the center of the stage. On 75m it is an automatic KO because the opponent is brought up to the top platform, very close to the stage boundary. On Pirate Ship it can also OHKO, but only on Jigglypuff. It will also OHKO in the World 1-2 version of Mushroomy Kingdom.

At the beginning and middle of the move, Ike yells "Great...AETHERRRR!!" (in the Japanese version, he shouts, "DAI...TEN...KUU!" which can be roughly translated to "Great Aether"). Due to the fact that Ike moves to the center of the stage when this move activates, on some created stages the downswing can be somewhat of a Sacrificial KO. As with a standard Aether, Ike tosses his sword up into the air, and jumps after it, before attacking his foe in mid-air. It can be noted that the site of impact, following Ike's final descent, is determined by the character(s) closest to the ground directly below them.

CPU opponents tend to get hit by this move, even if not caught in the initiation. When they try to "add to the woes" of one caught in the move (as Sakurai suggested at DOJO), they don't understand to get out of the way, when Ike plummets down, and get caught in the explosion.

Trophy Description
''Ike's Final Smash--a powered-up version of his signature move, Aether. Ike faces a foe and swings his sword up for a hit, then tosses his sword into the air, performs multiple nasty strikes, and finally unleashes a mighty overhand blow to send his opponent plummeting down. It's a very impressive sight, but if Ike misses with the first upward swing, he can't use the move.''

Origin
Oddly enough, this move has never been seen before in the Fire Emblem series. It is possibly a reference to a recurring event in Ike's games known as the "Trial of the Blue Flame", where the goddess of order would be awakened and purge the world of life. However, the flame in Great Aether is regular flame, not blue.

It could alternatively be a reference to the final blow given to Ashera at the end of Fire Emblem: Radiant Dawn, where Ike uses Yune's Power.

Trivia

 * Interesting to note, when Ike first appears in the Subspace Emissary, he uses a regular Aether on the Ancient Minister, but he yells out "Great Aether". Maybe because the voice of the final smash sounds more heroic, as the way he appears.
 * Ike's Final Smash can be canceled, as can Toon Link's Triforce Slash, by attacking at the right time.
 * Mr. Game and Watch can use his up aerial to make those trapped escape the hits of Great Aether by pumping the trapped upwards. This also happens if a Poké Ball with Latias and Latios or Kyogre is sent out right before the Final Smash is activated.
 * As with End of Day, it is possible to self-destruct with this Final Smash if it is used on a custom stage that has a gap in the center.
 * There is a glitch that can be done when fighting Ice Climbers. When having the Final Smash without being activated and fighting Ice Climbers with high damage gauge, he can grab the leading Ice Climber and throw him out of the stage (or by some other ways, but the important thing here is to kill the leading Ice Climber first), and then quickly unleash the Great Aether on the second Ice Climber. The previously KO of the leading IC will cause the second to disappear, but Ike will still use the Great Aether, resulting in Ike slashing and hitting the air with the Great Aether.
 * Great Aether is a OHKO on 75m, Mushroomy Kingdom stage 1-2, and on certain custom stages (if they have a floor in the center that is close enough to the upper blast line)
 * Great Aether is a One-hit KO move dealing 300% damage on two stages in two specific situations - on Spear Pillar, by using it when the beam of light is firing down the center, and on Norfair, by using it when the wall of lava has gone halfway across the stage.
 * If the player is on Frigate Orpheon and the Final Smash is used while the stage is turning it will freeze in its current position.
 * The move consists of 2 full vertical slashes downward, 1 vertical downward slash stopping short, 1 stab, a horizontal backhand slash, another vertical slash, a horizontal forehand slash resulting in a spin allowing him to kick his enemy/ies twice, a backhand downward diagonal slash, an upward vertical beginning a spin that allows him to make 2 more upward verticals and then flip to a charge position with Ragnell above his head before making the final vertical slash downward to the floor, resulting in a total of 14 hits excluding the initial strike.
 * Despite this being Ike's final smash, it is actually only his third most powerful attack, KO power wise. Both his Eruption and his forward smash can launch opponents farther, if they are charged enough. Great Aether is his most damaging attack however, dealing almost twice as much damage as a stage 8 Eruption.