Heart of Leviathan is encountered as the level boss of Mission 8. The primary goal for this fight is to kill the main Heart before or during cross laser pattern.
Vergil trivializes this with his Yam Aerial Rave + PS. Dante must have full Rage-meter RG before entering the fight. Although, there are many dynamic situations that can occur due to Envies movement.
Only Dante can kill the Heart before cross laser pattern using using Aerial Cross JC's.
Although, it is not always guaranteed because sometimes one of the envies can be too passive on approaching the player.
This case is usually possible when attempting BanHeart or sudden double damage surge from RG + DTE.
It's possible to dodge the laser while maintaining the DPS with delayed Aerial Rave and well timed jump.
This is an example of Flux Release granting more damage than it usually does.
It's important to remember that BanHeart release varies on DT gain so, sometimes it may not grant enough symbols back to charge for DTE kill. Therefore, Dante will have to opt for Old Heart ending.