A criminal was someone who committed a crime.
There were several Foamasi criminal organisations, including the West Lodge, Dark Peaks Lodge, South Lodge and Twin Suns Lodge. (TV: The Leisure Hive, PROSE: Placebo Effect)
The Elective was a criminal syndicate within the Union, based on Hexdane. (PROSE: The Crystal Bucephalus)
Kane and Xana were part of a criminal gang on Proamon. When they were going to be arrested, Xana killed herself rather than face a trial. Kane was exiled to Svartos for his punishment. (TV: Dragonfire)
The word "crook" was a slang term for criminal. US President Richard Nixon famously declared that he was "not a crook" during the Watergate scandal. (PROSE: Tricky Dicky [+]David Llewellyn, The Brilliant Book 2012 fiction (BBC Books, 2011).)
Before becoming the Tenth Doctor's companion, Majenta Pryce had been a member of a criminal group called the Crimson Hand. (COMIC: The Crimson Hand)
Dirk Slipstream was a criminal who served time in Volag-Noc after being caught by the Doctor. (PROSE: Night of the Humans)
Beep the Meep was the leader of the Meeps and a galactic criminal who referred to himself as the Most-High. (COMIC: Doctor Who and the Star Beast)
Kerko was a Blowfish criminal who came to 21st century Cardiff via the Cardiff Rift. (PROSE: The Undertaker's Gift)
Prior to coming into the employ of River Song, Nardole had been a criminal, a period of his life he sought to make amends for. (TV: Oxygen, The Doctor Falls)
By Time Lord law, Renegade Time Lords were considered criminals. (PROSE: A Brief History of Time Lords)
In the Unbound Universe, the Ke Le Divisions were composed of criminals that the Master had brainwashed with his Keller Machines. (AUDIO: Sympathy for the Devil)
When the Fifteenth Doctor revealed to Lindy Pepper-Bean that he had unblocked himself after she had blocked him from communicating with her on the social media service known as the Bubble using his sonic screwdriver, she described him as his companion Ruby Sunday as criminals. (TV: Dot and Bubble [+]Russell T Davies, Doctor Who series 14 (BBC One and Disney+, 2024).)