Killer Cat is a strong and fast pushing Black enemy, somewhat similar to Gory Black in behaviour, but with few knockbacks. Luckily, it has Single Target, but spawns in huge groups in The 222 Incident.
Strategy
Thanks to their Single Target attacks and short range, it is not too difficult to get many of them clumped up by using lots of meatshields; this often results in them being easy targets for Bombercat and Ring Girl Cat, who are both able to easily neutralize the threat posed by groups of Killer Cats. In general, any meatshields + midrangers approach works fine too, though that depends by the circumstances.