The problem of this objective has been discussed several times on the forums. It’s absolutely infuriating to loose an objective and a good rank because you’re unlucky enough to face a creatureless deck.
Now, we theorically have the option of killing our own creatures … But whats the point? It’s totally counter intuitive and a good part of our removal spells are now only able to destroy oponents creatures anyway(which is Also pretty annoying when objectives force you to delay the end of the game).
Objectives that depend on oponents build should just be gotten rid of.
There is a large-enough sub-theme of providing an advantage for destroying your own creatures, it would be fine to ask players to build for it once in a while, or at least allow it to happen in the existing Destroy objective since it is already worded like it should count self-sacrifice.