This Seeking Tech guide will explain how you can quickly beat Retro Rampage 2 in Astro Bot.
Use the following video as a reference:
For the first step, hold Square to ready your spin attack and stay in the middle front part of the arena. Afterwards, sidestep the spit attack from the slime and then use your spin attack to destroy its core.
To deal with the bunny enemies, stay grounded and sidestep their attempts to stomp you. You can then attack them when they land.