These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Altering the combat system drastically to resemble its competitor
Ignoring things that happened in previous games
Releasing an Obvious Beta and taking more than 6 months to release the game outside of Russia. The disc-based North American copies were literally unplayable for over half a month after release, and only became playable after getting codes by e-mailing the company and participating in DRM invented just for these players.
Game Breaker: The undead in the second game have the werewolf, who is impervious to any nonmagical attacks and can be bought pretty much right off the bat, as well as units that prevent your entire team from making an action, and some of the strongest front line fighters in the game.
The melee units for the Undead Hordes are arguably stronger than the Empire's in Disciples 1 and 2; their Mage line is even more likely to be the better one among all the races, as it contains the damage powerhouse that is the (arch)Lich, the healer-by-combat Vampire, and the game breaking Deaths. Paralyzer units were a great boon, and the support units (undead dragons) weren't too shabby either. All this contributes to a strong case that unit-wise, the Hordes dominate. On the other hand, their magic system is a mixed bag. Alongside a rich selection of damage spells with the widest variety of elemental sources (a plus) it contains inferior versions of the curse spells available to the Legions of the Damned. The first three summons compare unfavourably to what other sides can field, and they have pretty much only one booster spell, albeit a very good one (Damage Ward).
Conversely, the Empire and the Mountain Clans have some of the best booster spells and healing spells available. Unlike damage and debuff spells, which can't target units in towns and capitols (and the stronger units have wards and immunities anyway), boosters and healing are always useful. The Empire and Mountain Clans also have spells that increase mobility (the Empire's spell restores half a party's movement points, and the Mountain Clan's removes the steep movement penalty of sea-travel). If the player chooses to be a Mage Lord, these spells can be researched for half the cost and cast twice a day.
The Son of Ymir may very well be the most powerful unit a player faction can produce. And unlike the rest of the Mountain Clans' units, it's also relatively fast. And it's only a level 4 unit.
Jerkass Woobie: Bethrezen, really. He was imprisoned for something that was entirely not his fault.