You will need: Macho Cat , Wall Cat , Samba Cat (Can be replaced with other meatshields), Paris Cat / Sexy Legs Cat , Dragon Cat , Mythical Titan Cat , True Valkyrie Cat, Crazed Bahamut Cat (Unknown Cat). You may not have these cats, and you may not need them, but note that this stage will be significantly HARDER without them. Use Wall Cat as a staller. When the 2 Master A get close, spawn Bahamut Cat, spawn all of your units and spam your meatshields. If you have a long range Uber like Radiant Aphrodite/Megaphrodite, it is recommended to replace Bahamut.
Strategy 2 (W/ Gacha Units)
What you'll need: Macho cat/ or Samba cat, Tank cat, Artist cat, Giraffe cat, Paris cat (or Sexy Legs if you don't have Paris), Titan cat, and then long range units that can out range Master A. Hacker Cat is good, and any long range Ubers (I used Kachi-Kachi because he attacks fast and recharges pretty fast as well, but he has 460 range which is only 10 more range than Master A so if he pushes you back even a little he could potentially kill Kachi-Kachi) So if you have any ubers with 470+ range bring them. You can bring Crazed Bahamut but Master A out ranges him by 1 so he will only get a few attacks off before eventually being killed. But you can bring him to do some big damage to the Master A's if he is able to get a few attacks off. Fast attackers are good for Master A because they're able to get a few hits off before dying.
What to do: As soon as the battle starts, 2 Master A's are spawned and a lot of Those guys, Snache's, and Doge's spawn so as soon as it starts send out your meat-shields and spam Artist cat. After about a minute or two Duche's spawn so send out Sexy Legs/Paris when they do to deal with them. While stalling Master A with your meat-shields and Artist cat, save up your money until you send out hacker cat, then stall again until you can send out your long ranged ubers (or vice versa, whatever floats your boat). Once you have Hacker cat and your long ranged cats out start sending out Giraffe cat & Titan cat to do some extra damage to Master A. Oh and also here's a Pro Tip: Make sure your meat-shielding is on point otherwise Master A will push you back (and really.. nobody wants that). So make sure you protect your long ranged units and eventually you'll get rid of the Master A's and win the stage.
Line up: Two worker cat start level up combos (optional but will make things faster), Awakened Bahamut Cat (yes, I finished into the future before doing this stage), Cyborg Cat, Jiangshi Cat
Start the stage by releasing a few Jiangshi Cats and Cyborg Cats. Once no peons are shielding the boss, release Awakened Bahamut Cat. Bahamut will be knocked back once at 3-star and 4-star, but he'll live. The boss should be dead after two hits from Bahamut (if he is at level 30).
Replacing Cyborg Cat with Manic Macho Legs would be much easier due to its wave attacks, but sadly it cannot be used at the 4-star stage.