He penned a sorrowful note to the family of his 21-year-old victim Aiia Maasarwe, days after the details of her horrific fate were made public.
Herrmann beat the international student over the head with a metal pole at least 13 times, raped her, covered her in flammable WD-40 spray and set her body on fire at Bundoora in January.
"I'm sorry," Herrmann, who has pleaded guilty, wrote in a handwritten letter read to Victoria's Supreme Court by lawyer Tim Marsh on Thursday.
He said there was "no excuse" for what he'd done.
"Your daughter didn't deserve such a terrible and tragic thing."
"I don't expect any forgiveness as I will never be able to forgive myself and I will be trying to make amends for the rest of my life.
"Don't give in to hate like I did."
Prosecutors want Herrmann jailed for life for the "vicious and violent and depraved" attack which showed a "complete and utter disregard for the humanity of the victim".
Mr Marsh said Herrmann - who had a severe personality disorder from extensive childhood trauma - was not a monster despite his monstrous crimes.
Justice Elizabeth Hollingworth is expected to sentence Herrmann on October 29.
