It's called Brightburn. Names have been changed to protect the innocent, but it's perfectly clear who this is supposed to be based on.
EDIT: Technically, Gunn is just the producer, but he clearly played a large role in making it.
“About a year ago my brother Brian, my cousin Mark, director David Yarovesky, producer Simon Hatt and I started coming up with an idea for a horror film that excited me in a way nothing outside of Guardians has in years – it was personal, and different, and perfectly suited for our times. And, yes, terrifying.”