Nazo´s appearance change very much. His pupils and iris is not visible and the whites turns red, the black market around his eyes turns blood red. His fur turns from light blue to black with purple stripes. His gloves and socks turns light purple and the shoes turns pink.
Since Nazo is not a true biological life form, he could possibly handle all 7 World Rings, unlike Sonic, who only uses 3 to transform, all 3 of which are embodiments of negative emotions (Red - Rage, Green - Hatred, Purple - Sadness), the other four being mainly positive. (Yellow - Joy, Blue - Pleasure, Light Blue - Prayers, Grey - Wishes)
From absorbing all 7 World Rings, Nazo's power has skyrocketed. He is possibly able to outmatch even his Super Perfect form, as just 3 World Rings gives a similar power boost as 7 Chaos Emeralds. (Darkspine Sonic near equal to Super Sonic) Otherwise, his abilities are pretty much the same.
In this state, Nazo takes on a more aggressive persona - he will attack relentlessly, and will attempt to slaughter anything in his way. His voice also takes on a more aggressive edge, making his voice deeper and rougher. He also has a habit of roaring and powering up in an apparent rage, although it seems to come from nowhere half the time.