Splatoon/The Ravenous Octomaw!

To unlock The Ravenous Octomaw!, the player must complete all six missions of Area 4. The Boss Kettle is on a platform in the center that must be accessed via Inkrail.

Walkthrough
The Octomaw fight takes place on a platform in the middle of a "lake" of purple ink with four pipes rising out of it. The boss itself, at the beginning of the fight or after a respawn, will start in the pipe directly across from the level start. It will then proceed to use this cycle of attack:


 * 1) Octomaw swims through the ground to the Inkling's position, opening its mouth underneath the spot in a large circle, instantly filling it with purple ink. At this point, the Inkling needs to get outside the "fence" of teeth that have appeared (if not already out, see bullet point below). After a few seconds, Octomaw will snap its mouth shut, instantly killing the Inkling if they're still there.
 * 2) *The Octomaw will not curve to get to the player; it will only target where they were when it began to charge. If it misses, it will open its mouth at the edge of the stage.
 * 3) Octomaw will then sit upright and smile at the Inkling for a few seconds, offering free shots at its teeth.
 * 4) Next, Octomaw will dive under the platform and swim to one of the pipes. Afterward, it will launch its teeth like rockets, each stopping in midair to fire a shot at the Inkling before returning. The teeth can be destroyed in this stage.

Octomaw will continue this pattern until it has no teeth left, in which it repeats this pattern without the teeth-launching attack until the next phase of the fight is achieved.

To reveal its weak spot, the player needs to simply throw a bomb in Octomaw's mouth while it smiles. This is easier to do with fewer teeth left, so the player should destroy as many as they can. After taking out the first and second tentacles, Octomaw replaces its teeth with what appears to be iron and gold teeth respectively, gold taking the most damage overall.

One of the quickest ways to defeat the boss is as follows: Once the battle starts, the Inkling will be facing the enemy. Spray a path of ink 45 degrees to the right, and as soon as the boss charges, swim out of its way using this new path. Once the teeth pop up and the Inkling in the clear, turn around and start shooting at the teeth, quickly moving from one tooth to the next as you destroy them. The boss should get up and smile at you, and at this point, you probably knocked down one to three of its front teeth. If the player has a good shot at the hole, lob a bomb, otherwise, use this smiling period to open more teeth. Only two or three teeth need to be extracted before a clear line of throw is revealed. You should be able to damage it before it does its pipe attack. Repeat the same steps for every stage, and you should eventually succeed.

In addition, a single Splat Bomb will instantly destroy all teeth in the first and second phases (provided it has enough blast radius upgrades), providing an easy shot into its open mouth. The third phase requires two Splat Bombs instead.