Well, "completely" - is a hyperbole.
You can count Gekko as 0.5 of a Mexican Valorant agent or as 0.1, or as 0.00001 but he is definetly not a 0 Mexican.
China has 2 (Sage + Iso)
USA has 3 (Brimstone + Viper + Gekko) and Mexico has 1 (Reyna), though you could technically consider Gekko Mexican (he's from Mexico but lives in Los Angeles so he's considered American)
I don't remember exactly—all I really remember is he has a direct connection to Mexico. I think he also has a slight Mexican accent, though I might just be imagining it
Gekko's is the most well-known but we know the cities of some other VALORANT agents as well. Off the top of my head, Cypher is from Rabat and Raze is from Salvador
Then there's Omen and Vyse who are unknown, and KAY/O who's not only unknown but also from an alternate timeline
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