Isildur's Fateful Strike
The type line is the wrinkle worth reading the card for. Instants almost never gate their own casting, but this one does: it functions only when you already control a legendary creature or planeswalker. That restriction is the whole trade. In exchange for narrowing when the spell works at all, the effect runs richer than a clean four-mana kill spell would: plain destruction of a target creature, plus a hand-attack rider that scales with how greedy the opponent has been. The exile clause only bites when they are holding more than four cards, and it strips down to exactly four, so it becomes a punishment for the sculpted, hand-heavy hands that control and combo decks depend on. Empty their grip and the second half does nothing; let them stockpile and the removal doubles as a hand-strip in the same breath. The design logic is coherent: a spell that rewards a board full of commanders and superfriends by folding black's hand disruption onto black's kill spell, both effects landing on one card and both locked behind the same legendary payoff. Note what it does not do: this is ordinary destruction, so indestructible, regeneration, hexproof, and ward all still apply. The power is not in the removal being unstoppable; it is in stapling a hand-exile punisher to a removal spell you can only reach once the legendary requirement is satisfied.
