I have gotten every other achievement in this game besides these ones. I need help. Gamertag: Sifakis
200k is doable as one guy alone. I used the Dare crater - (Has been a while, forgive if I misword anything...) Anyhew - the closing doors are an unequalled opportunity to stick it to them. The war chieftains are the biggest problem. Main thing - use the hammer and keep the fuel rod. Only use the fuel rod if you must.