Stagflation is stagnant output plus inflation. Not something you will see in a deflation.
In a deflation the economy will stall or go into a vicious spiral of ever declining employment and output. A negative feedback loop.
That's an utter myth. It's never happened in America, even pre-Fed, which is most of our economic history.
There has never been a deflation spiral in America. Prices reset, risk ratios return to order and investors re-enter the markets, many bargains make new fortunes once capital is correctly allocated.