Ares

He is 50 feet tall, and his mouth would be 3-4 feet tall. The feet would be 6-7 feet long, and would be dirty and smell like fish. The crab can talk. Give him a young adult male voice, just like a normal human voice. For how he would be able to use the pincers, he just holds stuff in his claws. He's aged around 23 years old, in human years.

Regarding the civilization, it's full of crab giants who dine on flesh-based organisms and kelp. They have a kingdom ruled by a king and queen with an army of warriors. There are also shops and a tavern in the kingdom, as well. Both men and women treat each other as equals. Their civilization is probably hidden, invisible from the outside to normal people, but visible on the inside. Kind of like Wakanda, but in the deep ocean. Yep. So deep. As to what those crab people look like, they just look like Ares, except with different body shapes. The crabs are somewhere in between with regards to being aware of the micros underfoot. There are those that keep an eye for smaller folk, while others don't bother looking. They also have second language they speak besides English, maybe Pacific or Mediterranean, but most likely, it would be a mix of both. They live as an entire civilisation of crustacean titans, with the civilisation much like Atlantis for giants with Ancient Greek culture and architecture.

For example, a crab can take human women and girls, and torture them with the rancid odor of the stinky, dirty feet while stomping on them for pleasure. When it comes to torture, the crabs can force the victim to smell the feet as they slowly crush their body.