Haven't checked how it actually works but I think it's impossible because my guess the flow is (sorry if it's a bit technical):
1. Hit the enemies
2. Client (fgo on our phone) will calculate the damage
3. Call fgo server with the total damage and/or remaining enemies HP
4. If the enemy dead, fgo...
me lol on my quartz account. not sure what the cause was because after I installed the update, I logged in with my main account first then changed to my quartz account, and a few hours later that account got banned. now I installed the original fgo client with my main account and it's good so...