Which monster do you like the most in Heroes 5 (level 4)?

Not always is one upgrade the best throughout the entire game, or rather, not always does an upgrade fully reveal its potential with any number of units.

I didn't understand you at all. What did you want to say in this post? My opinion about upgraded units: they are naturally better than regular ones, but at the beginning, they are not always more useful (i.e., not for all units). For example, it's not worth upgrading human archers in the early game, but for the undead, I always upgrade skeletons first.