Next attempt at getting it I had damage and fire rate (meant that instead of speed last time) at 18, raised speed to 14 while running around, and it crashed on me... guess no badge or bonus for me.
Managed to reach the last level (didn't use mines, died on the last few bosses) but didn't get the badge either. Get as many flags as you can on the early levels as the extra points give you a huge advantage later on. I had damage maxed (18) and speed at 15.
If you did all 8 challenges but don't get the badge repeat challenge 8. I also did that before others and also had '7/8', but after repeating it I got the badge.
For those not planning to buy gold but wanting the hard badge: Work on your castle buildings from the start. The 't2' archers (Elven Rangers) make all the difference. Once you get those you can do all the regular mobs with 6 of those, and for bosses you can either stick to 6 or replace one with a dwarven champion to take a few hits.
Do arena battles from the moment you can, even if you lose you get honor points and at level 40 you can start buying some nice equipment with it. Also do all free instances and all bounty quests you can do per day (and use your free spin of course), and focus on defense on one defensive hero while making the rest balanced or attack. Blue or better instead, no white or green ones (although I completed it with one green hero, 4 blue and 1 purple, it takes longer to level a green one and they'll be weaker). Put those with high def at the front, and stick with the reinforced flanks formation for most situations.
I actually got over 50% before actually paying attention and noticing that those stats weren't added automatically but you had to actually drag and drop them to use them :D
Tip for those who want the hard badge: Cursed Werewolf gets huge regen and doesn't take much damage at high levels. Don't invest in Will or Int, and use one 50 or 55 res item per resistance. Two cold and fire items if you plan on trying to run through levels at top speed later on, that means the flame breath and cold chargers don't do damage anymore.
A save/resume would make this 5/5 for me. At level 13 or so I got the message that my wealth had reached a highscore, I clicked the link to check it, click the dropdown list open, and my browser decided that that meant 'refresh page'. All progress lost, didn't even get the medium badge as I hadn't died or finished the game...
Got all the badges, only hard part was finding out that you need those footsoldiers before the first boss. Once you have found that out the rest is only timeconsuming.
If you cannot get past the first level you need to experiment more with tower configurations. It took me some time too, but once you finished the first level it gets easier. You can get more skill points by replaying a level, making it even easier to do the next one.
Skill required?? Run back, buy nuke/flamethrower/jetpack, and run forward to kill the other. Real skill there. With 2 people doing the same it's simply a question of who gets bored first.
Well, I'll probably get the 15 points from the 50 kills later on, won't bother with the 1000 DNA probably. Also wonder why it shows 274 DNA available to spend, but claims I already have 446 of the 1000 DNA for the badge.