A gladiator was a type of fighter.
A Shad'ath gladiator was one of the many creatures captured by the Zygon warlords, Anktra and Kestral. They planned to carry out a traditional duel on the planet Shontaa, involving fighting to the death using this variety of host bodies. This duel was observed, however, by the Fourth Doctor and Leela, who found the Zygon ship and freed the prisoners. (COMIC: Rest and Re-Creation)
Sometime after the thirteenth Doctor, Graham, Ryan, and Yaz had visited an alien amusement park (COMIC: Meet the Fam!), the team discovered that their individual memories of the visit had been tampered with to the point of being inconsistent with each other. Yaz's memory of the visit saw the Doctor being put into the park's gladiator games after winning a test of strength game. (COMIC: Holiday Special)