Question: what episode does echo die?
Answer: Clone trooper Echo was presumed dead after the Citadel mission in Season 3. In Season 3, Episodes 18 through 20 — “The Citadel,” “Counter Attack,” and “Citadel Rescue” — a team of Jedi and Clone troopers head to the Citadel, an impenetrable prison where Master Even Piell was being held.