For this event the Assault cards are:
Hell Bike Ghost Rider: 1000% Boost base, 2500% Boost when fused.
Red Hulk: 500% Boost base, 1200% Boost when fused.
Wrecker: 200% Boost base, 600% Boost when fused.
Slasher Sabertooth: 300% Boost base, 1000% Boost when fused.
Chaos Magic Scarlet Witch: 250% Boost base, 700% Boost when fused.
No matter what people say. You need to take down the walls and these cards help you do it. Taking down a wall will give you double the points when defeating players than if the wall were still up. Because of this it virtually always makes sense to take down the wall.