Torched? Dragonfire, magma.
Sliced? Too common. Axes, swords, traps, claws, teeth...
Shot? Bows and crossbows are DEADLY.
Splattered? Drop trap.
Suffocated? Lungs damaged, upper spine damaged, submersion...
Impaled? We got it. Rotting? You better believe it. Slowly bleeding to death? Uh, duh. Skulls crushed? Yup. Ripped to shreds? Pretty much possible. Eaten? Well, worldgen-only, but it'll come into play. Hit by a minecart? Yup.
And it's not just the ways to die--there's also circumstances. Bronze colossi beating you to death slowly with your own gloves, goblins killing a baby in her mother's arms and only THEN lashing the mother to death, killed by a miserable wife, impaled by a unicorn, killed by a minecart carrying the bodies of your friends and family, paralyzed while a giant spider covers you in webs and rips your head apart, having your lungs amputated by a lousy doctor, having a baby thrown at you, slain by an infinite horde of Monsters Man Would Be Much Better Off Not Knowing, skin rotting off, frozen in ice, stuck in a half-flooded tunnel waiting to die, drained of blood by a vampire, strangled by a monster or several until you die of thirst, lashed to death, beaten with glorified sticks by heavily-armored dwarves while disarmed and fully armored, so as to prolong your suffering, crushed under a ceiling, dying by having stew thrown at you, being crippled and euthanized, lying on the battlefield (or in the hospital or prison) until you die of neglect, dying from untreatable infections from your wounds months after the fact, killed by carp, skewered by a friendly-fire ballista bolt, a number of these at once or in succession...there's no shortage of horrible ways to die. And that's ignoring the possibilities offered by modding.
Does your friend even know about DF? Or does he mean that you can't see the carnage?