Adaptive resistence.
This Golem gain's resistence to the damage type supplied to it for 1 minute. If it is attacked by the same type of damage over 3 more rounds it becomes immune for the round after that.

Immutable Form. The golem is immune to any spell or effect that would alter its form.

Alert. This creature cannot be surprised.

Multiattack. The golem makes two melee attacks.

Slam. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 3d8 + 6 bludgeoning damage.

Sword. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit:  3d10 + 6 slashing damage.

Calculate weakness. The Golem can take an action to calculate a particular targets weaknesses, it learns any vulnerabilities it has in that action.

Optimize attack. The Golem can use its bonus action to optimize one of its attacks this attack will either gain advantage or max damage, it cannot do both and it cannot use its multiattack feature the turn it does this.

Adaptive defenses. Once it has been attacked by an attacker, the Golem can negate one attack by that attacker in the next round. If the attack is a critical, it negates the critical but takes the regular damage.