The phrase "regret not only" is correct and can be used in written English.
You can use it when you would like to express regret for more than one action or thing. For example: "He regretted not only his behavior, but also the words that he had said."
This must be a matter of regret, not only because it diminishes the importance of a profoundly important branch of painting, but because it might discourage young artists from entering the field.
Then a few of my friends and my brother were preparing to go off to university – to bigger towns far away and even to London – and I began to regret not only the Dannimac, but almost all of the choices I'd made so far.
I felt a terrible pang of regret, not only as Georges but as myself, burning these things, standing next to that colossal heat of that bonfire and slightly singeing my eyeballs, I remember.
Core of this study are the common effects observed between the conditions IP and OP (after baseline subtraction), which indicate that vmPFC-ACC and hippocampal activations mediate the processing of regret not only when directly experienced, but also when knowing that someone else is facing a counterfactual negative outcome.
The means by which this occurs is not described in detail, but they claim that experienced regret not only helps us to remember our mistakes and missed opportunities and motivates us to engage in reparative action; by means of mental undoing it also prepares us to behave more appropriately when we are confronted with similar choices in the future (p. 13).
Travelling is never a decision I've regretted – not only did it provide me with some amazing experiences but it also landed me a great job.
Reading were left to nurse bitter regret, and not only for their dreadful defending in the first half.
Regrets is not only the title of all these paintings but is written on most of them.
"I still carry that regret, grief, blame, not only for him but for my daughters.
This is to be regretted, for it not only results in an overemphasis that destroys intellectual balance but it also has relegated to the background some of the more exciting aesthetic accomplishments of the Native American.
And the final paradox of Henry's Demons is that, even though there can never be a complete return from the farthest shores of madness, to lose a son (or brother) in this way entails not only regret and sorrow.
