With nero do some different combos with sword, devil arm and with sword in the air some time until you get smoking then use devil trigger and press circel, triangel and forward two or three times. That should fo it with him. Even easier with Dante, You don't need to use Devil Trigger. Just the same combos as Nero until sicking then attack two scaresrows at the time with swordmaster circel and R1 continue pressing circel so Dante do a powerful swordcombo. That should settle it. Other people who have other ways?