: Takes place two years after the original, focusing on a new protagonist, Shinn Asuka, and the return of Kira and Athrun as veteran pilots.
What fans commonly refer to as "Gundam Seed 51" is almost certainly the special episode titled: gundam seed 51
: The epilogue shows the characters settling into their new roles—Cagalli taking up her political responsibilities in Orb and Kira finding a quiet life with Lacus and the orphans at the Marshall Islands, setting the stage for the beginning of Gundam SEED Destiny Where to Find It Special Edition III : Takes place two years after the original,
– Kira in the Strike Rouge vs. Rolo in the Nephilim in an asteroid field. No beam spam — just tight, tactical combat. Kira disables the enemy by cutting off its power supply while quoting Lacus: “Fighting to protect means knowing when to stop.” No beam spam — just tight, tactical combat
Most likely, you are thinking of one of the following:
It sounds like you’re imagining a hypothetical for Mobile Suit Gundam SEED — perhaps an OVA, special, or alternate epilogue set after the original series finale (Episode 50, “To a Future that Promises Peace”). Here’s a feature concept: