When someone looks so good or if it is good, you'd say fitch.
Him1: Ayo man, your chain looks so fitch on yo neck, bro. No cap!
Him2: Thanks, man. I appreciate it!
When someone is so fuckin fat, you'd say fatch.
Him1: Ayo, that man looks fo fatch, his fat is even leaking out of his mouth!
Him2: That fucking hideous, man. Why'd you say that?
*That fatch: That's a misunderstanding, it's my saliva!