Start off by upgrading your wallet. When Doge Darks come close to the base, spawn a couple meatshields and a Crazed UFO Cat. Repeat this process until your wallet is maxed out.a few more Doge Darks will come out, so do the same thing again until your money is full. When it is maxed, spam meatshields, Crazed UFO, Macho Legs, Crazed Gross and other units. DO NOT SPAWN AWAKENED BAHAMUT AT THIS TIME. When the base is hit, the real problem appears: the Shockwave Scoundrels themselves, Bun Bun Symbiote and Berserkory. Continue spawning your meatshields and other units. Because of Bun Bun Symbiote fast attack rate, Berserkory should miss...a lot. In case Berserkory does strike with his wave attack, don't worry, he isn't going to wipe out your army immediately. After the shockwave has cleared, spawn some meatshields and Crazed UFOs, with some Crazed Gross's here and there. When the two enemies get reasonably close, spawn Awakened Bahamut. If you don't, this stage will be much harder and you may even lose.
Awakened Bahamut will most likely die quickly, but the good side is that Berserkory will (hopefully) die. After that, just continue spamming your units and Bun Bun Symbiote should die soon.
When Bun Bun Symbiote dies, spam your units and claim the victory!