Turtloid - First Visit - Nightmare

Acid Rain

In Any% All Stages you want to visit Turtloid first to get Zero. Not only does this stage let you do that, but this area contains two upgrades that aid the speedrun.

The nightmare area is a 2x6 section of acid rain, similar to the last section of the regular stage but taller.

Your objective like the rest of this stage is to destroy the 4 eyes then the rain generator, while rescuing the two listed reploids (There are more in this section if that concerns you).

Make use of X's charge shot to destroy the eyes from a distance (one full charge + a lemon), and get into the gate quickly.

Nightmare Zero

Nightmare Zero is weak to the Z-Saber. Using a standing slash will stun Zero, and he will teleport after a long flinch animation. Using a JUMP slash will do the weakness-damage to Zero without the flinch, meaning he will continue attacking (watch your health!), but have significantly shorter invincibility frames.