Diggernaut

The Diggernaut is a Chozo mining robot serving as a Boss in Metroid: Samus Returns. It wasn't featured in Metroid II: Return of Samus and is an original creation of the remake.

In the past
When SR388 was under Chozo control, the Diggernaut was the biggest mining robot constructed by the Chozo on the planet and was abandoned when the Metroid rebeled against their creator.

Encounter with Samus
Samus Aran stumble across a desactivated Diggernaut in Area 3 and reactivate it believing it to be a Grapple Point, the robot will destroy the rubble and stare at Samus before getting away. Samus then encounters it in Area 4 where the Diggernaut identify her as a threat and begins to chase her through the tunnels at the end of the chase, the Diggernaut will go away and leave behind the Space Jump.

Battle
The Diggernaut is then seen in Area 6 where it inhale a Chozo Statue and its item sphere, soon after Samus run into it again and this time it chooses to battle her directly. The Diggernaut attacks Samus from the background and will use its drilling arms as a mean to attack, the arms take most of the romm's space and Samus must use her Space Jump to avoid it. After this, its head will come in the foreground and fire rotating red lazer beam at Samus, she must take the opportunity to shoot either Missiles or Super Missiles at its head while avoiding the lazer beams. When the Diggernaut take enough damage, it will fall and plant its arms on the foreground, Samus must then use her Spider Ball to get at the center of one of its arm and use Bomb to damage it.

If done correctly the Diggernaut will slam its arms on the ceiling and make purple energy sphere fall down while targeting her with a laser beam. Samus can destroy the sphere and it will even give her Energy Capsules. The Diggernaut will then try to suck Samus in its grinder, Samus can use her Spider Ball to resist it while laying bomb for it to suck and take damage. It will then fire its rotating laser beam at Samus once again which is the best moment to repeat the cycle and damage it's second arm.

Since it is now unable to drill with it's arm, the Diggernaut will start slamming them onto the ground to crush Samus, the impacts creates shockwaves that can damage Samus. It will then fire two range of four laser in the room, Samus must jump between the gaps between the lasers to avoid them. After that, the Diggernaut will do its vacuum attack once more and this time Samus must lay bombs behind her to damage the Diggernaut as it is the only way to continue the fight, once it as taken enough damage, its head will come in the foreground, Samus must use her Spider Ball to get on its head and bomb the three bomb points. After that, the Diggernaut will fall down and try to get up but Samus will blast its head off. Samus retrieve the Power Bombs that the Diggernaut stole as a reward for defeating it.

Nintendo of America tweets
"Diggernaut, a giant Chozo mining robot, adds new danger and tension throughout #Metroid: Samus Returns."

Trivia

 * Several other robots of a similar design can be seen in the background of Area 3; smaller ones are also shown fleeing through the massive doorway in the cutscene prior to the Diggernaut's boss battle.