Thundermare

A pure alpha-strike engine wearing the body of a beater. The 5/5 with haste already hits hard the turn it arrives, but the enters trigger is what turns that into a finishing blow: it taps every other creature on the board, yours and your opponent's alike, so the only untapped attacker is the hasty horse pointed straight at their life total. The asymmetry is the whole design, because the trigger taps every creature except this one. The original printing carries that pedigree in its clarity; the trigger has no targeting decisions, no conditions, no fine print, just a board-wide tap a player learns to read as "swing now." It is the structural cousin of effects like Falter that strip a defending player's ability to block, except it does the work on the stack the moment it lands rather than asking for a separate spell. The catch is timing: with no flash, this resolves during your main phase, and resolving its trigger taps your own creatures too. So it is not a way to clear blockers for an existing board; it is the play you make instead of attacking with a wide board, when your other creatures cannot get through anyway and the only number that matters is how much damage the lone hasty attacker pushes unblocked.