[Red Blaster]

They are tough when you first start out because their defense is like 300,000 or something (if you don't break 300k you only end up doing 1 damage or whatever)
If you have cards with TPA that really helps put a dent in them. also monsters thst do direct damage, ignoring defense, with skills wreck them pretty easily since they only have like 14hp. Mass attacks really help too..basically just throw put as many attacks in the turns alotted.