Hey I've had a burning question in the back of my mind who are the apex predators of the underground minus all the main characters dogo,sans,undyne,metaton.

Let’s go by areas-

The only major predator within the Autumn Refuge anymore, where the Ruins of Old Home reside, is Napstablook. Sure, the little monsters still hunt each other, but Blooky is the one they all fear, and for good reason.

In the Frigid Arboreatum, the area in which Snowdin resides, there are many higher predators, mostly the remains of the Dog Guard and Sans, but Gyftrot also has a name for himself, with his insidious trap. Winterest, the large city to the north, is overrun by frost spiders as well.

Waterfall, along with its capital of Springhaven, is largely held under lock and key by Undyne, but Ragel, the Temmie horde, Onion-san, and Shyren also hold large parts of the swamp under sway.

Hotland and Summerset, its shining jewel of a city, is divided into three. Muffet, the former Royal Guard, and the Amalgams rule here.

The CORE is inhabited mostly by Mettaton, but is also haunted, and hunted, by Madjick.

New Home is prey to many common monsters, such as Burgerpants and Bratty, waging war on one another in an eternal battle for the highest ground and the best meat.