Gunfire Reborn

The Ichthyosaurus Offspring is the boss of the second World (Desert)

Its a giant, skeletal snake of sorts and has a few attacks which are:

Sweeping Laser - The boss will aim either left or right of the player and fire a laser from its mouth, sweeping across the battlefield - to dodge this attack, stand still and wait for them to pick a side, then move and dash the opposite direction from the laser. Being closer to Ichthyosaurus Offspring will reduce the distance you need to move

Bite - The boss will dive under the sand and disappear from sight, there will be a red circle where it will emerge and try bite the player in the circle, simply get out or dodge away from this cirlce

Rain of Poison - The boss will raise its tail and start shooting multiple balls of poison towards the player, to dodge this, stay out of the red circles on the ground where these balls will land and be careful of the pools of poison that linger where they land

Shockwaves - When the boss still has its tail raised and is finished with its "Rain of Poison" move, it will start slamming its tail down and send shockwaves out, simply jump over or dodge through these

The boss itself isn't too hard, just keep shooting at its mouth where its weakspot is and it will eventually die and you will get this achievement