The weakest castle in Heroes of Might and Magic IV!

Counter-pick? No, I haven't heard of that.
The same can be said about Chaos versus Order, and so on.

Well, look.
Death can fully utilize its potential, for example, against Chaos and almost 100% against Nature.
Against Life, Death is effective at around 40%.
Here.
But, as I've repeated, this is said from the perspective of Life.
And so, it's optimal for Death to build its army in this way against Life.
Skeletons (effective), Imps (effective (because they disrupt Angels by draining mana)), Cerberi (moderately effective), Souls (effective (they constantly age soldiers, requiring periodic removal of the aging effect, but the hero can be killed in the meantime)), Vampires (ineffective (too much ranged combat and Crusaders)), Mutants (moderately effective (by the way, I probably have a bug in my pirated version, but Mutants can be killed by poisoning them, both with poisonous attacks and with magic)), Devils (moderately effective (you can kill the hero or attack the crossbowmen, but nothing more)), Skeletal Dragon (ineffective (no one will shoot at it; they will simply attack with Crusaders and Marauders)).
As you can see, Death's potential against Life is very low.