Here is the full list of all 12 Yu-Gi-Oh! Millennium Duels achievements worth 200 gamerscore.
Completed Expert Mode.
Played 30 Multiplayer Duels.
Won 15 ranked Matches.
Used a signature creature against their owner.
Inflicted at least 1,000,001 damage.
Completed Yu-Gi-Oh! 5D's and ZEXAL series.
Completed Yu-Gi-Oh! and GX series.
Completed your first series.
Reached the top of the first ladder.
Completed your first Duel.
Won a Duel using a custom Deck Recipe.
Won a Duel and earned a second copy of a card.