Undercutting Axe

Weapon (handaxe), rare (requires attunement)

This weapon carved of stone is a favorite weapon of adventurous halflings, especially those that have befriended dwarf clans and fought alongside them against their oversized enemies. The wielder gains a +1 bonus on attack and damage rolls, and this bonus is increased to +2 against giants and against any foe that is at least two sizes larger than the wielder. When the wielder strikes such a creature, as a bonus action they can weaken the target. If the creature struck fails a DC 15 Constitution saving throw, it deals only half damage with weapon attacks that use Strength for 1 minute. At the end of each of its turns, the affected creature can attempt a new saving throw; on a success, the effect ends.

Once this ability is used, it cannot be used again until the wielder completes a short or long rest.