Deathgrip

As long as you can keep paying two black mana, no green spell ever resolves against you. That promise (a repeatable, uncapped counter that lives on a permanent and stays on the battlefield) puts the card outside the Counterspell lineage altogether. A blue counter trades one for one and walks away; Deathgrip is a lock piece, a permanent that taxes an entire color out of the game across multiple turns. The cost is what does the balancing: there is no upper limit on uses, only on your mana, so the card sells a permanent tax instead of a single exchange. The asymmetry is the point. Green, in the original color pie, was the color black was supposed to lose to (creature size, ramp, regeneration), so the early game printed a sideboard answer that flipped that matchup on its head. Lifeforce did the mirror job for green against black, Karma did it for white against black, Flashfires for red against white; the color-pair hoser cycle was the whole design idea, costed in mana rather than card disadvantage and narrowed to a single enemy color so it could not warp the broader metagame. Modern hosers are narrower in form and broader in target. Deathgrip belongs to a moment when a two-mana enchantment that said "you do not play green spells this game" was considered a reasonable thing to put in a starter set.