This is the correct way to finish the achievement HONORABLY DIE, INSECT!

Combo is pretty simple, you get a Mana Biscuit prior to your combo turn Majordomo Executus -> Conjurer's Calling -> Hero Power. To guarantee you're able to hero power atleast once it's best to play Tour Guide before to set up a 0-Mana Hero Power. 

Reckless Apprentice is there to clear some swarms of insects.

Auctionmaster Beardo to kill the prime insect with multiple hero powers face.