I have a tactic i used angainst most bosses.
I used Matt and upgraded my Sub and main weapon charges to Level 4, movment speed to 2 and bomb stock to 1.
Don't waste bombs on the monsters beforehand, save them for the boss. As soon as tha last monster leaves the screen, STOP SHOOTING! By not shooting, your main attack charges. when fully charged, fire your main, but only for a little while. When you get close as Matt Unleash sub attack for extra damage. Use your bombs when you think you are going to die, as they will remove ALL bullets from the screen. Keep doging bullets from the boss and eventually, it'll go down. Tested on Crab Battle with 3 life.
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