Minor SPOILER ALERT!
By the look of things that’s Blaise Zabini in the fiendfyre scene, climbing just below Draco. In the novel, Draco is accompanied by Crabbe and Goyle, but in the film I suspect Crabbe has been replaced by Zabini. (The actor who played Crabbe, like the actor who played Colin Creevey, is no longer in the Harry Potter films.) This makes me wonder if the death of Colin Creevey will be the death of that cute little kid Nigel instead. If so, I think it will be even sadder. Nigel’s a sweet kid, isn’t he? I hope they don’t kill him off. That’s all just speculation on my part, of course.