Hell Vanguard is first encountered as the level boss of Mission 2, but becomes a standard enemy in later missions.
Vergil trivializes this with his destructive Starfall and PS. Until Dante receives A&R or Beo for JC he has to start with clash release and Reb 1-2, Combo A then release with full RG Rage-meter and abuse Combo A.
The idea stays the same for both characters but they have to watch out for teleport attacks:
Dante have to Roll guard non-teleport attacks and regular release whenever it's possible.
This is ideal fight with Dante.
Ideal fight with Vergil