It's pretty much up to your opinion. In most ways they are 'evenly matched' in the games, but in reality, Shadow technically is more powerful. Sonic just has speed going for him. Shadow on the other hand has:
-Speed matching Sonic
-Chaos Control *with only needing one chaos emerald mind you. Sonic can only do it when Super Sonic*
-Chaos Control abilities like Chaos Spear, Chaos Blast, etc
-Agility
-And as far as we know Shadow doesn't run out of stamina as quickly as Sonic does.
So again it's kinda up to you. They are 'evenly matched' in most ways, but Shadow does have more abilities end of story xP
You have to beat him in a boss fight with Sonic.
there are alot of bosses with dr robotnik, and there are a few games called sonic the hedgehog, please specify.
Keep jumping on him and dodge his atacks
P. u have to go through the levels, beat bosses.
beat the death egg as super sonic and hyper tails
you have to beat the train staion level either sonic or silver.
With silver, pick up everything and chuck it at shadow.
Shadow - Beat Heroes story
use memory shard blue
you have to beat the story of sonic, tails or knuckles.
Yes once you beat the level Shadow's story is unlocked.
For The Last Boss For The Last Episode. (Beat Sonic, Shadow, And Silver's Episodes)
To beat Shadow using Silver, use Silver's telekinetic powers to throw objects and deal damage to Shadow.
Complete the Heroes Story (beat Jet The Hawk in Sand Ruins).
To unlock that difficulty you must beat the game with every character (sonic, shadow, silver.)
Just beat story mode with both the heroes and Babylon rouges.
You have to beat him in a boss fight with Sonic.