Epilepsy Warning: Whenever sonic uses his powers during the night he emits lightning that strobes. While this doesn't go on for very long it can affect photosensitive viewers.
Two people are thrown off a high tower building in an attempt to save them from Dr Robotnik. They are eventually saved but at the very last second.
Sonic is knocked out by an explosion. He ends up being fine.
At the start, Sonic's owl guardian/parental figure is shot in the chest with an arrow, then tell Sonic (a tiny kid) to run through a portal on his own. He runs, then turns back in time to see the owl about to be attacked by the same people who shot her moments back. He runs toward her, but the portal closes. It's implied the owl probably dies.
Toward the end of the 3rd act, Robotnik manages to knock Sonic out. His fur is roughed up and dirty. Everyone thinks he's dead, and Robotnik says they ought to get ice to keep the body cold (since he's said earlier that he plans to take Sonic to dissect.). That, plus the fact Sonic appears dead, could be upsetting to younger kids.
An explosion wipes out the whole town's electricity. The noise may be alarming to some.
Sonic pushes Tom and Maddie off a building, however he saves them afterwards.
Sonic Design from Trailer #1