Proteus Ridley

Proteus Ridley is none other than Ridley, who had recovered at least half of his organic body compared to his cybernetic self.

Biography
Having somehow managed to survive his defeat in the Pirate Homeworld's Leviathan against Samus, he managed to regenerate enough of his original body to not need at most half of his cybernetics.

Metroid: Samus Returns
When Samus is preparing to leave SR388 with the Baby, an newly hatched Metroid that imprinted onto her, Proteus Ridley unexpectedly arrives and proceeded to capture the Metroid, despite Samus acting quickly to prevent her old nemesis from capturing him. They then proceeded to do battle, with Proteus Ridley ultimately attempting to fly away. However, Samus grabs him by the tail and then the cybernetic space dragon proceeded to fling her in his direction, proceeding to blast him in the chest multiple times until he was forced to release Baby from his grasp. Proteus Ridley then attempted to intercept Samus as she retrieved the baby, but she then promptly blasted him in the wing, knocking him right into a nearby cliffside and causing rocks to fall on him while stunned. However, he regained consciousness shortly afterward and went on the assault on Samus. Eventually, he managed to get the upper hand against Samus, using his cybernetic right arm as a shield against her Arm Cannon and promptly throwing Samus against the cliffside before promptly pinning her down, planning to blast her with his flame breath at point blank range. However, the Baby suddenly proceeded to leech enough life energy from Ridley to restore Samus to full health, with Samus and Baby then proceeding to overwhelm Ridley until they ultimately subdued him. However, shortly after they left, Ridley left behind most of his cybernetics, including his mechanical claw, indicating that the fight ultimately had him regenerating fully.

Battle
The first phase of the battle has Ridley flying for the most part, also breathing purple fire either in an arc, or in individual streams. He also will at times try to jab Samus with his tail, and suddenly drop down to do a ground pound before taking flight. The weak point is in the chest area.

In the second phase of the battle, Ridley instead focuses on more ground based techiques, such as swiping at Samus with his claws or breathing individual streams of fire. If Samus jumps over him, he'll utilize his flight-based attacks, and will also upgrade his tail jab attack to have it forcefully cause the ground to emit spikes. He'll also have a new swooping attack in this form.

In the third phase of the battle, Ridley will have mostly the same attacks as before, although he will also proceed to rapidly spray fire as well as do a variation of his aerial fire attack where he shoots one blast directly to the ground and causes a shockwave, and also do a combination of his tail jab and swoop attack. For his ground attacks, he'll also utilize his claws to scratch at Samus. Timing your attacks right will have Samus blast him on the chest, then climb up and fire either missiles or beam blasts down Ridley's gullet directly.

Each time you do significant damage to him, Baby will proceed to absorb more of his energy. He'll be defeated the round after the second time Baby absorbs his energy.

After beating him each phase, he releases significant amounts of Aeion particles.

Trivia

 * Owing to him being a variation of Meta Ridley, he shares the same sound effects as him.
 * He wasn't in Metroid II: Return of Samus originally. He was exclusive to the remake.
 * His presence in the game was first hinted at in the Metroid: Samus Returns - Overview Trailer, where part of the Aeion gameplay portion has his theme playing in the background.

Other
The three phases to his battle theme are the following: The first being the standard theme that incorporates traits from both the Vs. Meta Ridley theme from the Metroid Prime series and the version of the theme from Metroid: Other M, the second phase having a more edgier tone with a more tense opening similar to that of the themes for Ridley from Metroid: Zero Mission and Super Metroid, and the third having a similar tense beat to the second phase, but with a more slower tempo, similar to that of the Neo-Ridley theme from Metroid Fusion.