Sonic Superstars

First you need to defeat the main story and Trip's story to unlock the final fight.

Tips for fighting the boss:

1- The falling rings, black holes and which helper character appears and when are random.

2- You don't need to use dash to attack the boss, except at the end. So try to save your rings and use dash only at the end or for getting out of the black holes.

3- Try to reach the 2nd part of the boss with 50 or more rings. You can do it with less, but it's more difficult, stressful and you need to use every opportunity to attack.

4- The blue donuts/iris attacks are mostly for delaying you on getting rings. So I didn't worry much about them and I prefer to go for rings instead of getting in the safe zone.

5- The last part of the fight, when the boss throws you meteors/fireballs, you need to send back 6 meteors in a row, evade the beam and hit the boss. If you fail in one of these parts, you need to do the meteors part again until you get it right. And in this part, the falling rings don't appear, so the only way of getting rings is when a helper character appears.

6- If you see the giant Flicky with Amy, this have priority. If I'm not mistaken, you can have 50 rings if you hit the 5 ring boxes

7- If Tails or Knuckles appears and if you are real close to them, you have extra rings (there is a golden light when you do it).

8- When the boss attack with the shadow claws, you can hit them.

And now, the video. Credits to Levas:

Going through YouTube to find an adequate walkthrough video for this boss was honestly just as frustrating as the boss itself. So I did as much research as I could and eventually came up with my own guide, describing every part of this fight from start to finish, so that there's no confusion and that you'll have a solid grip on what to do and how to finish this fight. Skip to 10:33 for the full walkthrough itself, as the beginning is an opinion piece. You can vote negatively if you like, that's fine; I honestly just did this so I could sleep at night.