Mono-Green ramp wants to flood the board with mana dudes and big threats like Craterhoof Behemoth, so small evasive creatures like Faerie Miscreant and Mockingbird fall behind on board stall. Languish is excellent here, wiping their Elvish Mystic, Llanowar Elves, Badgermole Cub, and Vastlands Scavenger at -4/-4 (though it misses bigger threats like Craterhoof Behemoth and Titan of Industry). Duress can't take creatures, so it won't stop Craterhoof Behemoth directly, but it can strip Nature's Rhythm, which is how they tutor up their biggest threats, or a Tail Swipe that would otherwise kill one of your creatures. Prioritize keeping Thoughtseize and removal to control their curve before they overwhelm you with mana creatures.