9. Imprisoning and then killing his brother
The Judge System was created in 2031 by Eustace Fargo, who served as Chief Judge until his attempted suicide in 2051. Fearing the loss of their leader the Judges implemented a cloning program to preserve his, and other notable Judges, legacy.
Several clones of Fargo were created over the years, most notably our protagonist Joseph Dredd and his brother Rico Dredd. Joe was the perfect Judge; Rico wasn't. In Prog 30 we learn that Rico was corrupt, committing multiple crimes including blackmail and murder.
Upon learning of his brother's crimes Dredd has him sent to a penal colony for corrupt Judges on Saturn's moon Titan. On Titan the prisoners are mutilated to be fitted with breathing equipment rather than waste a space suit on them. Naturally Rico isn't too happy with all this and vows revenge on his brother.
Eventually returning to Mega City One Rico attacks Dredd whereupon Dredd shoots him dead.
Familial bond doesn't mean much to Mega City One's toughest lawman.