Heroes of Might & Magic III: Horn of the Abyss

Well... if we don't talk about the graphical implementation, then the eighth level is primarily about imbalance. Some players like it, but for multiplayer, it's definitely unacceptable... (one player upgrades, say, 25 archangels to some super-duper archangels, and that's it - the stack becomes exactly twice as strong, which means there are 50 angels - quite a bonus, to say the least :) )