I need some tips on appealing and unique character design for my antagonist, Odium.

As the title suggests, I need some tips for unique and appealing character design, so that I can use them to create a great design for my antagonist character, Odium, on my own. He's an anthropomorphic, bipedal, non-pony OC and I need some tips on how to give him a design that matches his personality, fits into the show's universe, and is visually distinct and interesting. Sorry if this is too much to ask and if I'm being too vague, though.