Warforged Guardian

Legendary Resistance (2/Day). If the Warforged Guardian fails a saving throw, it can choose to succeed instead.

Siege Monster. Warforged Guardian deals double damage to objects and structures

Multiattack. Warforged Guardian makes two melee attacks.

Pummel. Melee Weapon Attack: +4 to hit, reach 15 ft., 1 target. Hit: # (3d10 + 5) bludgeoning damage.

Heavyweight. When the suit is subjected to an effect that would move it, knock it prone, or both it can use its reaction to be neither moved nor knocked prone.

Warforged Guardian can make two legendary action per round.

Beam Blast.  (Costs 1 Action). A 20ft line of fire erupts from the monsters gauntlets, each creature within the line must succeed on a DC 15 Dexterity Save or be dealt 3d6 Fire Damage on a failed save. 

Flash Bang. (Costs 2 Actions). Each creature in a 15ft sphere originating from the monster must make a DC 12 Con save or be blinded for One Minute. The creature affected by this affect may repeat the save at the end of each of their turns.