source: http://www.nicovideo.jp/watch/sm21697879
Updated with Shigekiyo (Fatty) and Yoshikage Kira.
Video shows the HHA and GHA for all of the characters available thus far.
Heart Heat Attack (HHA): A dynamic and cinematic super attack that costs one bar of meter. It's performed with a fireball motion + any two attacks.
Great Heat Attack (GHA): A character's ultimate attack, overlaying the character models in a manga panel style. Costs 2 bars of meter. It's performed with a fireball motion + all three attacks. Alternatively, it can be performed by just pressing the L1 button when using the default control scheme. A GHA can't be cancelled into from a Special Move.
System mechanics taken from: http://ls57tiger.freepgs.com/Joomla2_...