As Krokodil points out, death in the adventure strips was very common. In Dick Tracy, Chester Gould killed off bad guys all the time, usually in very gruesome ways.
But I assume that astorian is referring to major, sympathetic characters. In that case, no comic strip death has ever been as wrenching, affecting or heartbreaking as the loss of Farley the sheepdog in Lynn Johnston’s For Better or For Worse. The heroic pooch suffers a fatal heart attack after saving April from drowning.
“I didn’t think a heart that big could stop beating.” <sniffle>
Some of them die pretty graphically.
**The Brow- ** impaled on a flagpole Breathless Mahoney - (Madonna’s character in the movie) died in prison Flattop- his clothing gets caught on a spike beneath a ship and he drowns Gargles- Tracy puts him through a plateglass window and he’s cut to pieces Mumbles- 'nother drowning Sphinx- crushed to death beneath an elevator Shakey- slowly froze to death while attempting to elude Tracy Mrs. Volts- stuffed in an oven and asphyxiated by gas
Especially in the early strips, Tracy gunned down a good many henchmen, lackeys, and gunsels. The bizzarre deaths were set aside for major characters.
The strip John Darling was about a small-town anchorman who always longed to hit the national six o’clock news. In the last, out-of-the blue, strip, he got his wish: He was killed, and his murder was reported across the country.
Interestingly, many years later, Les Moore of Funky Winkerbean (written by the same fellow) ended up solving the murder.
For other examples, I think that the grandparents in Family Circus (who now occasionally appear as ghosts) were once alive, and I think a grandparent died in For Better or for Worse, too.
Actually, Shakey was the one I had in mind when I typed “unnerving.”
He was hiding from Tracy and the cops underneath a pier in what we should probably assume was Lake Michigan (while Tracy’s hometown was never specified, there are lots of Chicago hints).
It was the dead of winter, and the breakers that washed in over him slowly froze and entombed him in a suffocating icy grave.