Mega Bat

Mega Slime is a ground boss in Deep found in the last story level (Level 20). The PC version of the game has the Mega Bat's HP set to 7 but because of the difficulty, the mobile version's Mega Bat boss has 6 HP.

Developer Tips: How to kill the Mega Bat?
To kill the Mega Bat we suggest starting the boss fight with full health or with minimum 2 HP because of the tactics needed to defeat the Mega Bat. When you enter the boss room, try to hit as many melee hits on the bat as possible. When bat attacks you and makes damage, use the cooldown to land melee hits. Try to make at least 3 hits when the bat is waiting.

Mobile tips
When fighting the boss on mobile, use the up arrow to jump rather than using the X button because your left hand should be used to make melee attacks. (The mobile version has Bat's HP set to 6 rather than 7 on PC)