MooX 12 Jul 2015 07:50

I think that the correct description should be "Defeat both forms of the Nightmare without taking damage and losing life" because you can't perfect the first form and then die and retry the second.

ShadwSonic 11 Jan 2016 04:53

Fortunately, if you happen to do this during Boss Rush it still counts!

CarlosC 5 Oct 2018 20:00

MooX is right.It has to defeat both forms on a single play. Somebody need to fix it.

Paladincecil 3 Nov 2019 04:07

I'd avoid doing this on RetroArch. Didn't work for me there. Did work fine with the same Rom on RANes.

jared6502 15 Oct 2021 15:52

Make sure that when you complete the fight with King Dedede, you finish it without a powerup. Dying once at the start of the first phase might also be enough.

GrayCloudSpectator 10 Mar 2022 08:35

didn't trigger for me. Didn't die and never got harmed. However, I beat Dedede with 5 HP left, but it got filled up to 6 HP when the first Nightmare boss started. Also didn't use a power-up in Dedede fight.Edit: switched to QuickNES core and the achievement was unlocked when I completed the boss rush mode - I entered the first form with 3 HP left.