Here is the full list of all 30 Counter Spell achievements.
Reach level 20 with a Priest.
Reach level 20 with a Warrior.
Reach level 20 with a Mage.
Reach level 20 with a Shaman.
Reach level 20 with a Warlock.
Complete 50 quests in Quest Mode.
Enter build mode.
Enter build mode with more than one player.
Kill an enemy player in a PvP match.
Kill Cinder in any game mode.
Reach level 20 with a Rogue.
Kill Lord Roderick in any game mode.
Reach level 15 on any character.
Kill Cillian in any game mode.
Kill Goldglom in any game mode.
Complete 20 quests in Quest Mode.
Reach level 10 on any character.
Kill Sir Nigel Gresley in any game mode.
Kill an ally with a grenade.
Complete 10 quests in Quest Mode.
Kill Chester Bolingbroke in any game mode.
Reach level 5 on any character.
Complete 5 quests in Quest Mode.
Kill Skitter in any game mode.
Kill one of your allies.
Kill Monoculus in any game mode.
Revive an ally.
Kill Cinder on hard difficulty.
Kill Cinder on insane difficulty.
Level any Permadeath character to level 20.