If you have the true form of Cat Machine, this will be a "GG Nyandam". You will first want to kill the Le noirs and Teacher Bun Bun with any strong attackers like Catman, A. Bahamut, Megidora...etc. Send in cat machine when le noir is dead, and hopefully, you will reach lil nyandam.. When Cat Machine reaches him, send in A. Bahamut. He will land a few hits, and dies, and by the time that happens, likely all you ubers will die...BUT don't worry!!! Cat Machine will still be alive and remember to meatshield and keep sending in good attackers like Cyborg cat, Jamiera cat, Crazed Whale cat...etc. Then, send in another Cat Machine when you can. By the time when the second Cat Machine reaches the first Cat machine, Nyandam will only have a few percent of health left. Finish him off, and there! You win!
As mentioned above, the classic Awakened Bahamut + Cat Cannon interrupt can do a good chunk of Nyandam's health. Be sure that the troublesome Le'noir is taken care of, or else he can lay waste to Bahamut in no time. With proper stalling and enough time, you can defeat this meddlesome child via rise and repeating.
A quantum blip de-aged him back to a kid. People don't know what to think when that leathery face cries over candy, but he still has to pay full price at the movies.