No serious violence for the most part. The occasional bit of schoolyard fights/bullying, and some scenes of mild injury, but nothing severe. No gore.
Hunter's father is said to have been killed in what's implied to have been a murder by drowning during a fishing trip.
Alex often worries aloud that if the chemical plant caught her, they'd "cut her up". In various episodes her fears are proven to have some backing. When Vince catches a monkey infected with GC-161 named Oscar, he excitedly says to Danielle, "we'll have to cut it open!" Danielle says in one episode that she wants to see the effects GC-161 has on cells and organs.
In the 4th season, the day Hunter is first introduced, Louis Driscoll mentions "fetal pig dissections" and brings in a live pig on a leash "to make a statement". The pig isn't harmed.
There are disturbing mentionings of scientists being killed off in the 1970's under mysterious circumstances ("BMX" episode) and Chappy the hobo is knocked unconscious by Vince.
Danielle Atron is rumoured to have been the victim of child abuse during a Halloween-themed episode.
An unnamed woman suffering from heat stroke falls unconscious; her body is seen on the ground on-screen briefly.
An elderly teacher trips and falls on top of a man.
A hamster dies and Robyn falls into grief over it.
A girl is abandoned at a demolition site and nearly killed.
A man cries out in pain when a radio is played loudly over his ears.
Vince is mentioned to have no friends and to have been frequently beat up in school.
Kelly is chased by a moving construction vehicle, and Alex and Ray laugh at her instead of helping her.
A doppelganger of Alex knocks Ray over by zapping him in the chest with electricity.
A boy is incapacitated with electricity in a truck.
A boy is trapped under a concrete pipe.
Alex's foot is squished under a dump truck.
A rabbit "morphs" into a puddle, and much to Lars' horror, the rabbit can't reform itself and is permanently stuck this way. He fears that humans who eat the chemical will end up this way, too.
Lars tries to blow up and kill George Mack with an improvised explosive. George survives.
Alex mentions pulling out a frog's intestines with tweezers.
A morbidly obese girl shows adverse health issues after trying a drug.
A girl is chased home and threatened with hockey sticks.
A man tells Vince that he'll "burn you so bad your teeth will melt".
Alex frisks a woman and threatens Vince with a baseball bat.
Vince falls from a ladder and injures his neck. He then later gets electrocuted after accidentally placing his hand on a bug-zapping machine that kills insects.
Lars and an unnamed chemical plant employee both receive electric shocks that mildly impair them for a temporary period.
A man falls into a pile of hay and horse manure.