I can't figure out how to get this stupid trophy for killing 10 enemies in 10 seconds using the Gravity Typhoon -__-
Might had the same trouble as me. I think you have to actually hit the enemies and kill them with the projectiles. I was too close and I threw people around. So I had to fly up in the air and then fire from above.
I did my trophies with the Diabolically Yours side mission. The one where you have to protect the ship with Fi. There are red crystals to fill up your meter.