The flyers imposed Hudak's image over top of the Joker character from the Batman movie "The Dark Knight."
With just 24 hours until polls open, Liberal Steven Del Duca took to Twitter to say he was sorry to Hudak, calling the flyers "a mistake."
But deputy PC leader Christine Elliott calls the flyers a deliberate, "sickening" attack, and says it was fear-mongering at its worst to scare voters into voting Liberal.
She says such tactics should be beneath the Liberal campaign team or any politicians.
The Liberals and Conservatives are believed to be in a virtual tie heading into Thursday's election.
All three leaders are putting in one final push on the last full day of campaigning, with Premier Kathleen Wynne staying in Toronto but focusing on NDP and Tory-held ridings.
NDP Leader Andrea Horwath has stops in Mississauga, Brampton and three ridings in Toronto, plus three ridings the NDP does not hold in Oshawa, Belleville and Kingston.
The Tory bus also starts out in Mississauga, but Hudak then heads south to Waterloo, Niagara Falls and Jarvis, where he'll wrap up his campaign with a town hall meeting.