When a teacher asks you to "comment on a character," the teacher is asking you to describe the character. It's a fairly open ended question, so you can comment on the character's physical appearance, personality, or both. You could even describe whether or not you like the character and explain why.
Raghu is the main antagonist of the story, at least according to Ravi. One for sure thing that the reader knows about Raghu is that he is hairy. It's brought up a few times actually.
—but he hadn’t much faith in his short legs when matched against Raghu’s long, hefty, hairy footballer legs.
I also believe that Raghu is a fairly good athlete. Ravi brings up the footballer thing twice, and the second time the reader learns that Raghu is a champion footballer. His size isn't directly told to the reader, but I am under the impression that Raghu is a bigger kid than most, if not all, of the other kids. He's faster than they are, and every time that Raghu moves, Ravi describes it like a lumbering ogre or giant.
Ravi had a frightening glimpse of them as Raghu combed the hedge of crotons and hibiscus, trampling delicate ferns underfoot as he did so.
Lastly, I think Raghu is a jerk and bully. He's not nice to other kids. He's chosen to be "it," and the first thing that he does is complain and accuse everybody of cheating. When he finds the first kid, Raghu calls him an "idiot." Then, there is this description:
. . . and then stalked off in search of worthier prey, whistling spiritedly so that the hiders should hear and tremble.
Obviously Raghu takes perverse pleasure in having the other kids be afraid of him. That's what bullies are like.