Who exactly are these guys? Well Cloud is a soldier while Sephiroth is Cloud's Darkness. Tifa is Cloud's light. So why is Cloud avoiding the light and fighting the darkness? He wants the darkness to be gone because he can't yet handle the light in his past. But Sephiroth says you can't handle your own darkness, so what makes you think you can handle the light? Cloud yells for him to shut up but Tifa yells "Cloud!" which makes the light come out hurting Cloud's head, but he wasn't hurt by light but darkness.