This card would be a perfect fit
Carnivorous Death-Parrot, Vile Bile, The Fallen Apart, Paper Tiger, Scissors Lizard, Rock Lobster, Double Header These Un-cards are considered mainly for pauper cubes since their power to toughness isnt special in cubes that allow for rares, but four power and a decent toughness for four is actually pretty hard to find outside of a few cards like Rhox Brute, Wildheart Invoker, and Windrider Eel (which is actually a 4/4)
Making Karlach unblockable for the turn after her first attack means that any subsequent extra combats shes just unblockable
This is particularly devastating with Goblin Javelineer, a card I cannot recommend you play but will see you play regardless
Life drain, card selection, and resilient reanimation create constant pressure that scales exceptionally well in multiplayer environments