This one is not bad at all....Pets unlock at the end of level 5. Buy the cheapest one. Shooty pet I believe. Simply don't let him get hit from levels 6 through 15. I focused on only buying smart bombs and droid power. If you feel your pet is about to get hit, just use LT for the bomb. I can confirm the checkpoint at the end of level 10 works. If your pet doesn't get hit until level 11, kill yourself, and you can continue at the start of level 11, with the pet, and opportunity to still get the achievement.