Both Receptionist 2 and Charles have Armor, the newest ability in Undercards, and are currently still the only monsters with Armor.
Armor (x) reduces the damage taken to this monster by x. So because Receptionist 2 has Armor (2), all damage it takes will be reduced by 2. That makes this monster very useful, despite it just having 2 HP, as it needs two attacks from a damage of 3, or one from a damage of 4 or higher, just like Mad Dummy.
It also has Taunt, so it must be targeted by monsters. But because it has 2 ATK, it's weak to Muffet's Pet.
The best way to deal with this card is Silencing it with Nacarat Jester or Scarf Mouse. You can also use Muffet's Pet, as previously mentioned. Tsunderplane and Papyrus can also instantly finish it off.
Both Receptionist 2 and Charles have Armor (2), as well as 2 HP. So both need the 2×3 or 1×4+ damage to die.