Vexing Beetle

A 6/6 for five mana that can't be countered: that is the reward, and the condition attached to it is among the most demanding the game has ever stapled to a beater. The +3/+3 only switches on when no opponent controls a creature, a far narrower window than it sounds: the opponent can hold lands, artifacts, enchantments, and planeswalkers all day, but a single token, a single blocker, or a single mana dork on their side deflates the beetle back to its printed 3/3. Against any creature deck that empty-of-creatures state is something you have to manufacture, typically by wiping the board and deploying the beetle before they can rebuild. The uncounterable clause is the tell about its intended home: this was built to close out a creatureless control mirror, where the opponent's side really is bare of bodies and the only thing between you and a resolved threat is a counterspell. Read that way the design is internally coherent: a finisher for the deck that has answered everything else, large enough to end the game quickly, immune to the one interaction a control shell still holds up. The trouble is that the condition and the body pull against each other in practice. The matchups where you want a hard-to-counter beater are the ones where the opponent has stopped casting creatures; the matchups where they flood the board are exactly where the bonus never arrives.