24: Basically every single episode has at least one dose of wham in it, the whole series is practically built on it, and some episodes take it to almost absurd, shocking levels.
Day 1, "5:00 - 6:00 a.m.": After several episodes helping Teri Bauer track down her daughter Kim and his daughter, Janet York, "Alan York" (Kevin Carroll using an alias) goes to Janet's room and smothers her to death.
Day 1, "7:00 - 8:00 p.m.": Victor Drazen is not only not dead, but he's the high-value prisoner Andre is trying to rescue - and he's played by an uncredited Dennis Hopper.
Day 1, "11:00 p.m - 12:00 a.m.": Jack, thinking his daughter is dead, goes on a rampage and kills Victor and Andre Drazen. He later learns that Nina Myers killed Jamey Farrell, and after stopping her escape from CTU, discovers that she shot and killed Jack's wife, Teri.
Day 2, "10:00 - 11:00 a.m.": Jack goes undercover with a terrorist cell to bomb CTU, and simultaneously attempts to warn everyone about the attack without breaking his cover. He fails, and it's utterly demolished resulting in several casualties. Oh, and current CTU Director George Mason gets infected with a lethal dose of radiation poisoning and now has less than a day to live.
Day 3, "6:00 - 7:00 a.m.": After an hour of "will he, won't he", Jack executes CTU Director Ryan Chapelle in a trainyard.
Day 5, "7:00 - 8:00 a.m.": A group of assassins succeed in killing former President David Palmer and Michelle Dessler, seriously injure Tony Almeida, and almost kill Chloe before Jack heads back into the field to rescue her. Notable in that the fatalities occur before the first commercial break.
Day 5, "6:00 - 7:00 p.m.": A terrorist succeeds in activating a nerve gas canister in CTU, killing off most of the personnel inside the building (including Edgar Stiles, who collapses and dies as Chloe, Jack and Kim watch).
Day 5, "7:00 - 8:00 p.m.": Lynn McGill goes out in a Heroic Sacrifice to ventilate the nerve gas from CTU, while Tony Almeida "dies" after unsuccessfully trying to kill Christopher Henderson.
Day 6, "9:00 - 10:00 a.m.": Jack is forced to fatally shoot Curtis Manning in order to save Hamri Al-Assad's life. Then, after he calls Bill Buchanan and tells him he's out of CTU for good, a nuclear bomb detonates in Valencia, California, killing tens of thousands - and there are four more devices just like it.
Day 7, "10:00 - 11:00 p.m.": Tony and Jack attempt to infiltrate and recover the Starkwood pathogen from where it's being shipped. Everything goes to hell: Tony is captured, and Jack fails to keep the pathogen from being recovered by Starkwood... while being infected with it in the process.
Day 7, "1:00 - 2:00 a.m.": After chasing a fleeing Starkwood operative, Larry Moss learns that Tony Almeida (who was helping chase the operative down) is actually in league with the enemy - just before Tony smothers Moss to death.
The late-season Day 8 episodes that fundamentally shake up the entire series:
"7:00 - 8:00 a.m.": The "live feed" of President Hassan's torture and planned execution was pre-taped, and he's already dead.
"8:00 - 9:00 a.m.": Just after consummating his relationship with her, Renee Walker is shot by an assassin, and eventually bleeds out before doctors can save her.
"9:00 - 10:00 a.m.": Jack wants to go after the Russians now that he knows they're the true ones responsible for Hassan's murder, and in turn Renee's as well. And then President Allison Taylor meets Jack in person and it's revealed that she's sided with Charles Logan to protect the Russians and in turn the peace treaty she wants signed and orders Jack to stand down. Jack takes it really well, resulting in him going against his own country in order to get the perpetrators.
"11:00 a.m. - 12:00 p.m.": After interrogating her for the whereabouts of a data chip, Jack shoots Dana Walsh in cold blood and walks off, thus cementing the fact that he's past the point of no return.
"12:00 - 1:00 p.m.": Jack's morals continue to slide when he intentionally endangers an innocent person to get to Renee's killer, whom he brutally tortures and executes. And then he winds up discovering that Logan is in on the conspiracy.
"1:00 - 2:00 p.m.": Jack dons heavy armor and assaults Logan's convoy and Novakovich's safehouse by himself, which Chloe and Cole view as an act so reckless to everyone around him that Chloe reluctantly gives Cole the go ahead to take Jack out if they can't find any other way to stop him, and all the while it's revealed that Logan and Russian President Yuri Suvarov are collaborating to end President Taylor's treaty.