Sonic the Hedgehog 4: Episode I

This is a good trick to end the level quickly and get the achievement.
First collect and keep hold of 50 rings in any level (except boss levels) then jump through the giant ring at the end of the level to start the special stage.
The first time you play the special stage just finish it as normal (get the Chaos Emerald and don't worry about collecting all of the rings) so you can replay it on the level select.
On the second run, once you've collected all of the rings in the stage, instead of going to get the Chaos Emerald to finish the stage, hit one of exclamation mark (!) blocks to instantly end it. If you got all of the rings the achievement will pop.
I can confirm this does work as this is how I unlocked it.

This took me roughly around 20 tries. I have a few tips:

For the groups of 8 rings, try to make the path horizontal so you can hop through them, instead of free-falling. Otherwise you'll probably miss at least one, and going back for one ring repeatedly really messes up your time.

Also, be careful when passing through the transparent buoys. A lot of times I accidentally threw myself through them and missed a ring.

Finally, after passing through the first set of transparent buoys, instead of jumping around trying to get all the rings, just turn the world in one direction and try to free-fall around it. I found that to be the fastest way to get through without bouncing off all the bumpers.

Good luck!

As shown in the video below, Start any act and collect 50 rings. You will need to hold on to them until the end where you will see a big ring that you need to jump into. Then you will start the special stage where all you need to do is collect all the rings and finish the stage and you will get the achievement at the end.