An average peon that almost any attacker can handle with relative ease. The actual danger posed by 555 is the potential Aftermath of killing it: a level 1 Surge deep in your lines, which can be problematic if this enemy is present in large quantities or buffed to an extent.
Due to how its most dangerous feature is the surge that spawns far in front of him upon death, it is recommended to try and kill hordes of 555s long before they reach the enemy frontlines, making Crazed Sexy Legs Cat, TalentedDark Lazer and Jellycat highly recommended against it. While countering this enemy should rarely, if ever, be your priority, this same strategy can prove beneficial against most Akus with the Aftermath ability all the same.
This enemy can be seen as The Battle Cats counterpart of Shield Penan (the Metal variant of Penanggalan in YuruGeGe); both are peons that are only threatening because of the damage they cause when slain.
Due to its Aftermath ability, this enemy can release an Aku soul when dying instead of a normal soul. However, since this enemy's Aftermath only has a 50% chance of activation, it can have two different death animations depending on whether Aftermath activates or not. This is the only case in which this can happen.