Bastet isn't that bad. So long as you mainly use units with 10 hp or more she won't be able to really kill everyone off on your team. If you want a real broken card, then the legendary gnome guy is by far the worst. Something like 40 hp, splash, and he summons some 20 hp building that gives +3 damage to every enemy unit at the start of each turn. The two times I've seen someone play that card they completely wrecked me.