The phrase "awful effect" is correct and usable in written English.
It can be used to describe a negative or undesirable outcome resulting from an action or event.
Example: "The new policy had an awful effect on employee morale, leading to increased turnover rates."
Alternatives: "detrimental impact" or "negative consequence.".
"It was terribly sad to see, and to see the awful effect on Gary's mum.
And yet there is something frozen in the representation: the great striped cat has fixed three of its flexed paws in the hide of the rearing victim; the next frame (and Delacroix produced many frames of this contest) would show the awful effect of its first searing rake.
Seductive in their simplicity, yet so profound in their awful effect.
But the bill, as written, applies to contractors who cheat the government whether or not it has that awful effect [like that created by contractors such as Blackwater].
But these chemicals have awful effects on domestic water supply.
The stuff was new to me, but its awful effects I had seen for myself.
This would have unpredictable (but no doubt awful) effects on the ocean currents surrounding the continent.
Brief telegrams from Chicago, New York, and other towns followed later in rapid succession, and left no room for doubt as to the awful effects of the visitation.
Imaginative research such as that described in Singer's piece, coupled with proactive screening such as that now legislated by California, will be crucial in mitigating the awful effects of TBI.
I couldn't quote the judge, or even describe his response to the evidently awful effects of the local authority's mismanagement of the case on the child and mother.
Underneath its coterie glitter, it might just be a satire on the awful effects of letting women into Oxford, or on the dandyism of Zuleika's most despairing admirer, the grand Duke of Dorset.
