Multiattack.The giant makes two greatclub attacks.
Greatclub. Melee Weapon Attack: +9 to hit, reach 15 ft., one target.
Hit:19 (3d8 + 6) bludgeoning damage.
Rock. Ranged Weapon Attack: +9 to hit, range 60/240 ft., one target.
Hit:28 (4d10 + 6) bludgeoning damage. If the target is a creature, it must succeed on a DC 17 Strength saving throw or be knocked prone.
Fling. The giant tries to throw a Small or Medium creature within 10 feet of it. The target must succeed on a DC Dexterity saving throw or be hurled up to 60 feet horizontally in a direction of the giant's choice and land prone, taking 1d8 bludgeoning damage for every 10 feet it was thrown.
Reaction
Rock Catching.If a rock or similar object is hurled at the giant the giant can, with a successful DC 10 Dexterity saving throw, catch the missile and take no bludgeoning damage from it.