The Pilot episode of Smallville describes the population as 25,001 in 1989 and 45,001 in 2001. For such a small town, they seem to have an inordinate number of deaths. This article details the body count of each episode in Season Four. Serious injuries and other crimes are also noted, but only actual lives lost will be tallied. Likewise, although Clark saves people from various ill fates, his rescues will only be counted if death seemed reasonably certain. Since the death of a metahuman is not always certain, continual updates are expected.
Clark, Chloe, and Lois work to find the antidote to Dr. Fine's treatment and cure Lana and Brett. Lois is captured by Dr. Fine, and Clark tries to save her, but she uses her martial arts talents to save herself and Clark from the kryptonite treatments.
Clark saves Jason of being shot. Lex interrupts Jason Teague's assault on Clark, but he probably wouldn't have killed him. Lois saves herself from Chloe's assault by curing her of the love potion, but again, she probably wouldn't have killed her.
Clark's body-switch cures Lionel's liver disease. Martha saves Lex by using Kryptonite on Lionel in Clark's body. A violent prison riot took place, but it is unlikely that any inmates or guards were killed.
A patient at the Smallville Medical Center and a LuthorCorp employee died from exposure to a synthetic toxin which excaped from LuthorCorp while they were working with meteor rocks. Dr. Ford, Lex and Clark save Jason, Chloe, Lana, Martha and Jonathan Kent, Lex himself, and dozens of others by developing and testing an antidote.
A store clerk is serious injured by Hercules, but he survives and recovers. Shelby saves both Jonathan and Clark, then frees Hercules but gets caught himself. Clark saves Shelby and gives him a new home.
Dawn Stiles electrocutes her ex-boyfriend, but he survives and recovers. While possessing the body of a nurse, she injects her comatose body with enough poison to give herself a heart attack. She attempts to burn down the school full of students, but Clark and Jonathan work together to banish her to the after-life.
Brendan Nash kills Haley Timmonds, making an example of her to Lana and Chloe. When he tries to use his abilities on Clark, they backfire; he petrifies himself, then falls over a railing and smashes into pieces. His other victims, Wendell Johnson and Delia Watkins are saved. Lex and Lionel save themselves by escaping the custody of Jason Teague. Lionel shoots Jason, claiming he was saving Lex (although Lex had the upper hand at the moment), but Jason survives.
Lana kills Genevieve in self defense. Clark saves a little boy from a meteor strike, but Jason is killed. Lionel is shocked into catatonia. Chloe saves Clark by dragging him out of Lex's vault. Twenty-three people in total are killed, according to Daily Planet article viewed by Baern in Fallout.
Forty-five people died in Season 4.
There are 10 episodes this season where no one died.
By the end of this season, there are 31 episodes in the entire series where no one died. That's an average of approximately 8 episodes per season.
Clark saved Lana Lang's life three times123 and once from possession1.