High-Fat is a very large man with a disproportionate upper-body compared to his lower-body. He wears a dark blue onesie with light blue polka dots, which covers his hands. His helmet and shoulderplates are yellow and spiked, and he wears dark boots and a pink belt with a yellow buckle. He sports a brown mustache.
High-Fat's full view.
Not much is known about High-Fat's personality. Having taken part in Big Mom's plan to assassinate the Vinsmoke Family, he can be considered to be very loyal to his crew.
Abilities and Powers
He wields a large sword. He was also given a Walker for the purpose of assassinating the Vinsmokes.
He then joined the siege on Bege, and when the Vinsmokes join the fight he attacked them. Later, he saw Big Mom attacking the traitor. After the Vinsmokes exited Bege's fortress to provide the alliance with cover, he tried to shoot at them, and watch as his crew fought them. 
In the manga, High-Fat and his comrades were defeated by Nami using Zeus' thunderbolt during the chase in the Seducing Woods. In the anime, Jinbe defeated him in battle instead.
High fat is a substance with a high fat content, and as a term frequently used, it means cocoa powder, which has a high content in cocoa powder, fitting with the food-themed names of the Charlotte Family and Big Mom Pirates.