Learn Italian: È il tratto più estenuante che abbiamo mai percorso. - It is the most exhausting stretch that we have ever covered.

Tratto is a very versatile word! While it can mean a physical drawn line or a personality trait, in the context of a journey, road, or period of time, it translates to a "stretch," "section," or "leg" of the trip.

How does Italian build "the most exhausting" in this sentence?

To say "the most" or "the least" (known as the relative superlative), Italian generally uses the definite article + the noun + più (more) or meno (less) + the adjective. Here, that formula gives us il tratto più estenuante.

Doesn't mai usually mean "never"? Why is it translated as "ever" here?

By itself, mai actually means "ever". It typically translates to "never" only when paired with a negative word like non (for example, non abbiamo mai percorso). You will frequently see mai used as "ever" in questions and after superlatives, just like in this sentence.

I've learned that expressions like "the most... that" often require the subjunctive mood. Is abbiamo in the subjunctive here?