if any noobs are are wondering to get the hard badge you need to beat all 7 dungeons with 1 character. Not over time with or incarnations of characters.
There is a strategy I came up with for the harder levels with boss units and huge counter attacks. (With elves) Get to maximum mana, and send assassins, dryads, hunters, and phantom archers, but NOT TOO MUCH. If you do too much damage to the castle, they will send 5 counter attacks at once. Wait for them to send just 1 or 2, with maybe a boss unit that you can take out with the rain of arrows. As the counter comes, let it get in front of the castle, and send stronger units such as protectors and phantom archers. Then rinse and repeat. This strategy will work against the frog general too, just send only ranged units and hobbits against him. He cant move because he keeps attacking the hobbits, with 200+ archers pulverizing him. I don't care about getting rated up, I'm just sick of people saying it's impossible.