People who died in trigun that where important enough to mention of course this section spoils it for you but it's info.

Under the character's name is a list of whom they've killed and who killed them, if applicable. Only characters who have killed and/or die are listed here. Please note, this is not including manga.

Brilliant Dynamites Neon
Kills an unnamed sand steamer conductor
Never dies

Monev the Gale
Kills many unnamed people
Most likely killed by E.G. Mine(cause of death unknown)

Dominique the Cyclops
Kills several unnamed people
Most likely killed by E.G. Mine or Midvalley (cause of death unknown)

E.G. Mine
Kills Monev and Dominique, and a group of unnamed people
note: it doesn't actually show who killed Monev & Dominique, but since Mine claimes he did it, I'm going with him.
Killed by Raidei (stabbed with Raidei's katana blade)

Raidei the Blade
Kills E.G. Mine and several unnamed people
Killed by Nicholas D. Wolfwood (1 gunshot from handgun)

Hoppered the Gauntlet
Kills Varre, Jones, Rumina, Farina, and a few unnamed people.
Dies when he does a Kamikaze attack on the 2nd plant of Seeds City.
(hurls his body into the plant, shattering it)

Gray the Ninelives
Kills several unnamed people
Killed by Nicholas D. Wolfwood
(via several missiles and other heavy weapondry from cross punisher)

Leonov the Puppetmaster
Kills Brad, and several dozen unnamed people.
Killed by Nicholas D. Wolfwood (missle launched from cross punisher)

Zazie the Beast
Kills several unnamed people
Killed by Nicholas D. Wolfwood (1 gunshot to right temple from leg of cross punisher)

Caine the Longshot
Kills several unnamed people
Dies by Suicide (1 gunshot to head with concealed pistol)

Chapel the Evergreen
Kills Nicholas D. Wolfwood (while being controlled by Legato) and several unnamed people.
Killed by Knives (disinigrated in a sparking ball of darkness)

Midvalley the Hornfreak
Kills unnamed people. Possibly kills Dominique.
Dies by Suicide (sets off a bomb in his saxophone, killed by shrapnel)

Legato Bluesummers
Kills the shoemaker, Jeffery, Lucky and all the rest of Rodrick's Gang, and hundreds, possibly even thousands of unnamed people. Arguably, he also killed Wolfwood by forcing Chapel to do it against his will.
Killed by Vash (1 gunshot to head at point blank range with silver handgun)

Millions Knives
Kills Chapel, Joey, and Revnunt Buskus firsthand. Is also responsible for ALL the deaths that occur when various SEEDs ships explode, including Rem's death.
Never dies

Vash the Stampede
Kills Legato Bluesummers.
Never dies

Nicholas D. Wolfwood
Kills Raidei, Gray, Leonov, Zazie, and at least one unnamed person.
Killed by Chapel while being controlled by Legato.
(shot multiple times in stomach area via Chapel's split cross machine guns)

Joey
Kills Rowan
Killed by Knives (1 shot to head with laser-gun)

Steve
Killed by Rowan. (caused his chamber to malfunction, killing him in cold sleep)

Mary
Killed by Rowan. (shot multiple times with laser gun)

Law/Roan/Rowan
Killed Mary and Steve
Killed by Joey (blown out of airlock into space)

Brad
Killed by Leonov the Puppetmaster (shot multiple times in the back with laser-gun via the Jessica puppet)

Jeffery
Killed by Legato (Legato takes control of another person(unnamed), and forces him to shoot Jeffery)

Rem Savarem/Sablem
Inadvertantly killed by Knives
(Was still on the SEEDs flagship when it exploded. The explosion was caused by Knives. Knives originally intended for Rem to board the escape pod with Vash & himself.)

Revnunt Buskus/Lebnant Vasquez
Killed by Knives (gunshot to head with handgun)