The 41-year-old is the fourth man arrested by outlaw Crime Gangs Task Force detectives.
The bikie from Mile End has been charged with aggravated cause serious harm and aggravated robbery and will appear in the Adelaide Magistrates Court on Monday.
Police are still trying to identify a fifth suspect involved in the assault, which took place about 3.10pm on February 13.
The bashing victim suffered serious injuries including collapsed lungs, broken jaw, broken leg and other facial fractures.
He was also robbed of jewellery during the attack, which police strongly suspected was as a result of a falling out amongst Finks members.
Since the assault police have raided a number of locations and seized items for forensic testing.
Today's arrest follows a swoop by police on Friday resulting in the capture of three men over the bashing: cruiserweight boxer Mostyn Niemann, 26, from Hendon, Bozidar Cecic, 22, of no fixed address and a 20-year-old from Albert Park.
All were charged with aggravated cause serious harm and aggravated robbery and appeared in court yesterday.
Two are Finks members and one is a Finks associate.
Detective Superintendent John DeCandia, Officer in Charge Crime Gangs Task Force, yesterday appealed for public help to help identify the outstanding suspect.
"We are seeking information from the community, which can be provided anonymously, to identify and locate him," he said.
"The investigation is on-going and further arrests have not been ruled out.
"Gang violence will not be tolerated and we will take action to ensure that those responsible are arrested and made to account for their actions."