A Queensland prisoner who scalded schoolboy Daniel Morcombe's killer with a bucket of boiling water in a vigilante attack will be released on parole in late November.
Adam Paul Davidson, 31, pleaded guilty in the Brisbane District Court on Monday to torturing Brett Peter Cowan at the Wolston Correctional Centre on August 5, 2016.
Judge Ian Dearden sentenced Davidson to three years' jail but with time already served he will be released on parole in late November.
The court heard Davidson plotted and watched Cowan's movements for a month to find the best way to harm the high-profile sex offender.
Davidson poured a mop bucket over Cowan's head while the then 46-year-old was playing cards with other inmates, then struck him in the head with the bucket three to four times.
Cowan received superficial burns to 15 percent of his body and was treated in hospital to prevent infection.
Davidson told investigators he attacked Cowan for "a little bit of retribution" and he wanted him "to feel the pain like somebody like Daniel Morcombe has felt."
Judge Dearden said every person was entitled to be treated respectfully, no matter how appalling the crimes they had committed.
Cowan, 48, is serving a life sentence for abducting and murdering Daniel on the Sunshine Coast in December 2003.
The 13-year-old's remains were found in August 2011 after an elaborate police operation prompted Cowan to confess and lead undercover officers to where he dumped Daniel's body.