A man who suffered a double skull fracture when he was attacked in the street says he could permanently lose hearing in one ear.
The 35-year-old spent a week in hospital following the attack in Regent Street, Hinckley, where he was celebrating a friend's birthday.
He spoke about the incident to encourage witnesses to come forward.
"I don't know much about it at all. All I can remember is waking up in hospital and I didn't have a clue why I was there," the father-of-one, who lives in Leicester, said.
"I don't know exactly what the attacker did to me, but I have two skull fractures to show for it.
"I don't think he just hit me once – it must have been a sustained assault. I have a green belt in karate, so I've fought 15 and 16-stone men who have hit me as hard as they can without knocking me out."
"I know what this man has done to me and I'm worried he will do the same to someone else or even kill someone."
"I am speaking out about this because I think this man is dangerous."
He has lost 80 per cent of the hearing in his right ear and at the moment the doctors do not know if the damage is permanent.
He said: "It's very disorientating because everything sounds different and it's affected my spatial awareness.
"But the doctors have said I was lucky in some ways.
"I haven't suffered any brain damage and, because one of the fractures was close to my optic nerve, I'm fortunate my vision hasn't been affected."
Detectives this week released a CCTV image of a man they want to trace in connection with the incident, which happened between 12.15am and 12.30am on Sunday, February 17.
Detective Constable Rob Buckley said: "This was obviously an incredibly nasty attack for the victim, who spent over a week in hospital and is still recovering from his injuries.
"Please take a moment to look at this image and see if you recognise the man in the picture.
"He may have information which can help with our inquiries. So, if you know who it is, or it is you, please get in touch as soon as possible."
Contact Det Con Buckley on 101 or Crimestoppers on 0800 555111.