DS Games With Morally Ambiguous or Villainous Protagonists

Few DS games cast you as outright "evil." Most explore gray morality. Here are the closest matches:

Protagonist = Antagonist / Villain

• Contact (2006) — You play Professor, an alien war criminal manipulating a boy (Terry) to rebuild his doomsday device. Dark twist ending.
• Infinite Space (2009) — Yuri starts heroic, but choices lead to galactic genocide ending (player-driven).
• Devil Survivor / Devil Survivor 2 — Protagonist can choose Demon Lord / King of Bel routes: enslave/destroy humanity.
• Radiant Historia — Stocke's "False History" choices lead to catastrophic timelines (but canon path is heroic).

Antagonist as Playable (Brief Segments)

• Castlevania: Dawn of Sorrow — Play as Dmitrii Blinov (boss) in "Julius Mode" (unlockable).
• Fire Emblem: Shadow Dragon — Play as Gharnef in vs. mode only.

Morally Gray / Anti-Hero Leads

• The World Ends With You — Neku: Starts misanthropic, manipulative. Redemption arc.
• Persona 4 (not DS — Vita/PS2/PC) — Choices enable "Bad Ending" (accomplice to murder).
• Hotel Dusk: Room 215 / Last Window — Kyle Hyde: Ex-cop, cynical, brutal methods.
• 999: Nine Hours, Nine Persons, Nine Doors — Junpei: Manipulates, lies. True end reveals his complicity.

If You Want Pure Villainy

PC/Console: Overlord, Dungeon Keeper, Carrion, Destroy All Humans, Evil Genius 2, Tyranny. DS hardware limited "play the monster" scope.

For DS: Contact is the clearest "you are the villain" reveal.