The Red variant of Teacher Bun Bun is slightly smaller but with high health and very high attack power. Because he is a Red enemy, any strong anti-Red Cat can take him out in a short time. He is still Floating, so you can also use anti-Floating units for him as well.
He has 400,000 HP and an attack power of 9,287, making him only slightly stronger than Teacher Bun Bun in the Moon of Empire of Cats Chapter 3 (399,996 / 9,000).
If you have many anti-Red Cats, defeating this enemy will be easier than defeating his original variant. If you don't, it will be harder, for he has half as many knockbacks as Teacher Bun Bun.
The strategy for defeating the regular Teacher Bun Bun (see the video below) sort of works for this guy, but you can defeat him by spamming small cats while using stronger anti-Red ones to deal some damage.
Because he has almost the same stats as Teacher Bun Bun's, most cats will be just as effective against him, but Bath Cat works much better than Dragon Cat when facing him. Strong cats such as Bahamut Cat or Uber Super Rare Cats work just as well against him, too.