Score the rank of Gold in all the challenge missions.
Kill the Brutalisk with lava in "The Devil’s Playground” mission on Normal difficulty.
Kill a Stank before it kills anything on Hard difficulty.
Use the A.R.E.S. to kill the Brutalisk in the “Piercing the Shroud” mission on Normal difficulty.
Complete 25 missions in the Wings of Liberty campaign on Brutal difficulty.