The second charge of a threat to kill has been dropped for the lack of evidence.
Rudd, who originally denied the charges, is due to appear in a New Zealand court for sentencing on June 26. He was detained at his home in November 2014 and has been out on bail since then.
On Tuesday, the court heard that Rudd had fired a number of employees in August 2014 after his solo album failed to break through the charts.
According to the court summary, Rudd admitted that he had offered a hefty sum of money, vehicles and a house to an associate in exchange for having one of his employees "taken out."
Shortly afterwards, Rudd allegedly called the victim, threatening to "come over and kill" him.
"As a result of threats made by the defendant, the victim was genuinely very fearful for his safety", the court summary read.
If convicted of issuing such a threat, Rudd faces up to seven years in prison. As for possession of cannabis and methamphetamines, he could be sentenced for three and six months, respectively.
AC/DC was founded in 1973 by brothers Malcolm and Angus Young, who named their band after the abbreviation for “alternating current, direct current”.
The band is famous for hard rock hits such as Highway to Hell, You Shook Me All Night Long, Back in Black and Hell’s Bells. AC/DC was inducted into the Rock and Roll Hall of Fame in 2003.