Oozore

The Oozore is an elusive and mysterious being found in Pikmin Eco as both the final boss of the game, and the main focus of the game's story as the player is tasked to track the Oozore down and capture it for an anonymous commissioner. Its entirely body, while not completely specified, is made up of liquified metal, with two cube-like cores that keep the body together, and varying rings around the body.

In the end of the game, it is revealed that the whole reason behind the commission is to gather its metal to create weapons in order to hunt animals on the planet, the commissioner working for a hunter that tried to do the same thing.

Strategy
Throughout the game, the player constantly runs into trails of the Oozore in different areas, but none of these times you're able to actually fight it since it manages to slip away each time. In "Explorer's Exit", the cave in Crumble Quarry just before Mount Metal, the Oozore creates numerous metallic versions of previous bosses in order to fight against the player, but all of them are significantly weaker than the actual bosses. It will only fight against you once you corner it on Mount Metal.

Phase 01
Once the fight begins, it will attempt to attack you and your squad with a whip-like arm, which if missing the main target will cause knockback to your squad. Its body, thanks to its liquid metal, is highly toxic even to White Pikmin, and will poison all Pikmin types who get into contact with it. Both of its cores are covered inside the Oozore's body, making it, for a time, invincible. Occasionally it will spread its body out along the battlefield, but doing so will expose one of the two cores. Only Winged Pikmin are able to reach and attack the cores during this moment, and the Oozore will quickly retract itself after a few swarming hits.

Phase 02
After one of its cores are destroyed, its attack strategy changes drastically. It will begin leaving behind a trail of metal, making areas unable to be walked on for a good five seconds before disintegrating. Its main attack spreads a set of whip-like arms, and spinning around, spreading more liquid metal around the battlefield and potentially hitting you and your squad. Its only able to be damaged after releasing a wave of metal, which will briefly expose the remaining core to attack.