Never Give Up! is the last stage in Love is Sickness.
At this level maximum number of enemies is 3, and they are mostly Red. Stacking Eraser (Wall) cat, Captain (Pirate) cat and Brah (Bean) cats is all you need to complete this level. The trick is to knockback enemy without killing them, slowly destroying enemy base and you won't have to deal with Bore and SLOTH.
Strategy 2 (CHEESE)
Line 1: (this is optional) as many knockback combos as possible
Line 2: Dread Pirate Catley, and if you want, any other cats that knockback red.
This strategy abuses the enemy limit. At the start, lure those guys near your base and start spamming dread pirate catly. You should be able to kill those guys quickly. If you have a decent stack, it should constantly knockback the one horns, and the dread pirate catly stack should slowly destroy the base.