Save DC = 16
Multiattack.The giant makes two greatclub attacks.
Greatclub. Melee Weapon Attack: +8 to hit, reach 15 ft., one target.
Hit:18 (3d8 + 5) bludgeoning damage.
Rock. Ranged Weapon Attack: +8 to hit, range 60/240 ft., one target.
Hit:21 (3d10 + 5) bludgeoning damage. If the target is a creature, it must succeed on a DC 16 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 1d6 bludgeoning damage for every 10 feet it was thrown.