Here is the full list of all 14 Might & Magic: Clash of Heroes achievements.
Complete all main quest and side quest objectives in all Campaigns
Complete all bounty side quests
Complete all Battle Puzzles in each Campaign
Unlock all special units
Triple fuse an attack formation in battle
Win a battle in the Sylvan campaign
Reach a Hero level of 10 and max out all units to level 5 in any Campaign
Reach Level 10 in online multiplayer mode
Collect all artifacts of each single player campaign
Win a battle in 1 vs. 1 online mode.
Create a link of 5+ formations in battle
Win a battle in 2 vs. 2 online mode
Win a battle using any of the playable Villain characters.
Deal an additional 100HP of damage to the enemy Hero on the finishing blow.