STAR TREK: Arena - S01e20 "Human Versus Reptilian!"

For bringing hostility into their solar system, a superior alien race brings Captain Kirk into mortal combat against the reptilian captain of an alien ship he was pursuing.

When a reptilian alien race known as the Gorn destroys an Earth colony, the Enterprise comes under attack by the Gorn vessel.

Captain Kirk soon gives chase to the Gorn ship, leading them to an unexplored solar system, gradually (and dangerously) increasing speed.

Kirk prepares to destroy the Gorn ship until another race of powerful aliens called the Metrons stops them and forces both captains to face off in mortal combat.

The main purpose of this one-on-one duel is to solve their dispute, the winner will be released and the loser will be destroyed along with his ship and crew.