SONIC UNLEASHED

note: Having maxed-out characters will help you out with this (especially the night trials).

As with the other continents, you need to complete the following to unlock this achievement:

Hedgehog:
Time
Rings
Enemies

Werehog:
Time
Survival

All of the above have three levels.

For both Time trials, follow the first 2 videos below to the best of your ability.
There are 1158 rings in the day level, so the Rings trials should be easy if you don't get hit.
For the Enemies trials, make sure you keep an eye out for any enemies.
Survival gives you considerably more health for this level than others. Level 1 has you starting at full health, level 2 drops it to about 2/3, and level 3 give you 1/2 of your max health. When dealing with Fire Masters, throw a water barrel at them before attacking. Remember to shield when needed and enter Unleash mode to avoid damage temporarily. It also helps to know where enemies respawn and take them out with a charged punch.