"Jack Attack" Cheat in Red Dead Redemption: Undead Nightmare – Does It Work?

No. "Jack Attack" is not a valid cheat code in Red Dead Redemption: Undead Nightmare. The standalone expansion uses a completely different cheat list from the base game.

Undead Nightmare Cheat Entry

1. Pause → Settings → Cheats → "Enter New Cheat".
2. Type the exact phrase (case-insensitive).
3. Once unlocked, cheats appear in the list for toggling.

Working Undead Nightmare Cheats (Examples)

• be greedy only for foresight – All weapons
• i want it all – All outfits
• time to nut up or shut up – Infinite Dead-Eye
• smart like tractor – All horses
• better than my dog – War Horse

Full list: Red Dead Wiki – Undead Nightmare Cheats.