The most UNPOPULAR faction in Heroes 5.

The worst faction is definitely the Warlocks!

There's no need to bash the Warlocks! What makes you think they're so bad? Maybe you just don't know how to play them properly? For example, I don't enjoy playing as the Sylvan faction, but I don't think they're terrible because they also have their advantages, just like all the other factions. The key is to know how to use them cleverly!