A second man has also received hospital treatment for head injuries following the serious assault on the Carnmoney Road in the early hours of Monday.
The two victims were walking in the Coolehill Park area at around 1am when they were attacked by a man who is believed to be in his 40s.
Police said he may have been armed with a baseball bat.
The 43-year-old man remains in a critical condition in hospital with serious head injuries, while the second victim has now been discharged.
Robert Hill, chairman of the policing and community safety partnership in Newtownabbey, told UTV he is "disgusted" by what happened.
"It appears two men were coming home from a night out when they were set upon by people with baseball bats," he said.
"Somebody had to go and collect that from somewhere to come after these people and that is very worrying. It has been pretty bad. We've had a lot of bomb alerts, the attack on the police last week, so there's been a lot of unrest in the area."
Newtownabbey Mayor Victor Robinson said: "This is a brutal attack on two men coming out of Glengormley - 99.9% of the community do not want this trouble, they just want these people to go away, we don't want to go back to the 70s."
The Carnmoney Road was closed to traffic for a time on Monday while police investigated the scene however it has now reopened.
Anyone with more information has been asked to contact the PSNI.