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