Question

The __________ probably held the first gladiatorial games.

Answer 1

The Romans, because they were Gladiators, and it is called the Gladiator-ial Games.

If you want the full definition of a Gladiator, it's here:
"A gladiator was an armed combatant who entertained audiences in the Roman Republic and Roman Empire in violent confrontations with other gladiators, wild animals, and condemned criminals. Some gladiators were volunteers who risked their lives and their legal and social standing by appearing in the arena. Most were despised as slaves, schooled under harsh conditions, socially marginalized, and segregated even in death."

Answer 2

The romans held the first gladiatorial games