R.Ost is among the most well-equipped pushers in the game. He has fast movement speed, high health, and a rapid area attack that will shred your cats. As the icing on the cake he can do Critical Hits, which usually is the difference between whether or not he oneshots Eraser Cat, and does not have a trait making it hard to inflict status effects. He has five(5) knockbacks, so be sure to bring lots and lots of damage, as that's pretty much all you can do to stop him.
A Metal enemy that only appears in the Golden Week and Silver Week events. It drops less money and has the usual Metal ability of only taking 1 damage except for Critical Hits, but it has much lower stats all across the board and cannot perform Critical Hits itself.