The man has used various handles including @MisterE2009 and @JonVeee to threaten and insult writers and artists.
Writer Marz alerted his followers to the cyber bully, who left a disturbing comment on one of his blog posts.
Millar followed up Marz's warnings with a post on his blog highlighting the behaviour of the bully.
He claimed to have secured the man's name and address and asked for advice about pursuing prosecution in the US.
The Twitter user has threatened female creators and journalists with sexual abuse and in one case mocked a wheelchair user.
Millar later followed up his post, saying that he had engaged the services of a Los Angeles criminal lawyer.
"Again, I stress that readers shouldn't try googling the names he's using as innocent parties may get targeted," said the Kick-Ass writer. "He's using false names for the most part, as you might expect.
"His IP address is all that matters and we've nailed the clown. This is a police matter now."
"He's been harassing women for two years using male and female names," said DC Women Kicking Ass on Twitter. "I have them all and if anyone wants the list I have it."