Lock Horns

Charlotta Build here -
Weapon imbue :
Critical Hit Rate 9
Tyranny 7
Sba Sealed resist 4 (bad)

Sigils:
Alpha+
Alpha+
Gamma+
Gamma+
Holy Knight's Warpath
Holy Knight's Grandeur+Tyranny
Combo Booster + Potion Hoarder
Critical Hit Rate+ Stamina
Glass Cannon+ Cascade (cascade doesn't do anything for Charlotta here)
Supplementary V+ Aegis
Supplementary V
Supplementary V

Note: I took off war elemental specifically for this behemoth run. Replace glass cannon for war elemental and you can use this build in regular fights.

Strategy for the run:
It's quite simple The Charlottas are the main DPS' of the group so we don't do anything particularly special. You need a character(s) who generates sba really quickly (Cagliostro and Lancelot in this case) and someone who's able to CC behemoth (freeze from Lancelot). We use a 2 burst from Cag and Lancelot just after behemoth overdrives to give us enough time to break him and stop him from going into bloodthirst. When he gets back up we sba again to lock him down so he can't move and so the stage timer stops. If we delay him long enough we should be able to kill him by the time the burst ends. This was done without the Cagliostro or Lancelot damage exploit.