Zen-Aku

"I have been awakened to carry out 3,000 years of VENGEANCE!"

- Zen-Aku

Zen-Aku was a Duke Org, cursed ages ago and imprisoned within a wolf mask. When Master Org defeated Animus, Merrick took it upon himself to defeat his evil. Knowing that he did not have enough power to defeat Master Org alone, he obtained the cursed wolf mask and used it to summon the Dark Wild Zords. Although Merrick was able to defeat Master Org with the power of the Predazord, he was soon corrupted by the mask's power, allowing Zen-Aku to take control of his body. With his willpower failing against the curse, Merrick begged his comrades to destroy him before he destroyed them, but instead, they sealed him into a stone coffin in order to protect the world from Zen-Aku's power.

Centuries later, Zen-Aku was released by Nayzor to destroy the Wild Force Rangers of the present day. As Zen-Aku, he battled them on several occasions, proving to be more than a match in battle-even stealing some of their zords for himself-until the Power Rangers learned the truth about his past and helped free Merrick from the curse. As it turned out, Merrick's transformation was caused by the full moon, (similar to the transformation of a werewolf) and Zen-Aku's power was weaker during the waning of the moon and during lunar eclipses. During a battle, Princess Shayla realized that the power of the curse was connected to the Predazord and told the Rangers to destroy the Predazord to break the curse. With help from the Rhino and Armadillo Wild Zords, the Wild Force Megazord was able to destroy the Predazord, thus breaking the curse due to the power of the curse being connected to the Predazord.

Unfortunately, when the Rangers broke the curse that corrupted the Predazord, they also lifted the original curse that trapped Zen-Aku in the wolf mask. After regenerating his true form, Zen-Aku attempted to kill Merrick and absorb him to regain the power he'd had when they were bonded together. Princess Shayla revealed that the curse had split Zen-Aku's power among the mask, Merrick, and the Dark Zords; with the curse broken, it had all concentrated within Zen-Aku himself.

When the Wild Force Rangers finally convinced Merrick to accept their help, they were able to overwhelm Zen-Aku, but the Duke Org responded by growing in size. In this state, he overpowered both the Wild Force Megazord and the Predazord, deflecting everything they threw at him. Fortunately, Merrick used a pool trick he'd learned from his friend Willie to send the Armadillo Zord flying into Zen-Aku's face, destroying his horn and badly weakening him. Merrick then struck him with the Revolver Phantom, causing Zen-Aku to crumble to dust, seemingly defeated.

In the finale, it is revealed that Zen-Aku somehow survived and seeks redemption, just like Merrick. They are last seen in or near a forest, about to begin their journey together.