The Battle Cats - OS Graveyard [No Hermit]
The enemy limit is 2 so keep that in mind.
Four ms is required or you will get steamrolled.
Use Manic Leg (or Hermit) to slowly take out the Professor A and try to build up a few Worker Cat levels. Once Professor A dies, a slightly buffed Bun Bun will appear to assist the Bun Bun Black. They're both rather weak, so slowly build up attackers to continuously knockback them until they die.
Basics are Lv20+70
Manics are Lv40
Specials are Lv30
Drone - Lv40