So generally FTL Sans against relativistic reaction/FTL attack speed Gumball?
If FTL is legit, then you have a case to make (even if Gumball is up there with him attacking-wise, though I'm going to need specific numbers on that as the feat Gumball scales to - Patrick Fitzgerald (Penny's dad) throwing his sandal and hitting the moon with it - has been calculated to be 1.32c), but even then...
Gumball and Darwin have been able to operate without their souls (well, we see it in Darwin's case. Gumball implies it when he says 'at least yours wasn't going down') ever since Anais was born, so I doubt soul manipulation will have that much of an effect on them.