A single trigger of annihilator 4 would severely hamper the opponents resources more so than exiling the top twenty cards does
It doesn't copy whether that creature is tapped or untapped, whether it has any counters on it or Auras and Equipment attached to it, or any non-copy effects that have changed its power, toughness, types, color, or so on
It really shines alongside token generators or cheap merfolk to quickly rack up those triggers
If you dont control an Army, create a 0/0 black Zombie Army creature token first.) Illustrated by Slawomir Maniak Standard Not Legal Alchemy Not Legal Pioneer Legal Historic Legal Modern Legal Brawl Legal Legacy Legal Comp
Thats normal
Beyond that, it combos well with all kinds of cards, giving players a wide range of options