Vegeta
Killed by a Death Shot from Freiza.
Killed in an attempt to save the Earth. By Self-destructing on Buu.
Killed by Android 17 in the Future.

Piccolo
Killed by a Ki Blast from Nappa while saving Gohan.
Killed when Majin Buu blew up Planet Earth.
He decided to stay on the Earth before Bebi blew it up because he loved it to much.
Killed in the Future by Android 18.

Krillin
Killed by one of Piccolo Daimo's men.
Killed by Freiza's magic spell attack.
Killed when Majin Buu destroyed Planet Earth.
Killed in the Future by Android 17.

Gohan
Killed when Majin Buu destroyed Planet Earth.
Killed in the Future by Android 17 and 18.

Android 16
Killed by Cell stomping onto his head.

Android 17
Absorbed by Cell.
Killed by Future Trunks in the future.
Killed by Goku and Android 18 when he fuses with the 17 from hell.

Android 18
Absorbed by Cell.
Killed by Future Trunks in the future.
Killed when Buu destroyed Planet Earth.

Android 19
Gets killed by Vegeta.

Android 20(Dr. Gero)
Killed by Android 17.
Killed by 17 in the future.
Killed by Dr.. Myuu after he helps Dr. Myuu fuse the 17's to make Super 17.

Cui
Killed by Vegeta.

Captain Ginyu
Killed when Buu destroyed Planet Earth.

Jeice
Killed by Vegeta.

Guildo
Killed by Vegeta.

Burter
Killed by Vegeta after Goku weakened him.

Recoome
Killed by Vegeta after Goku elbowed and winded Recoome.

Chaotzu
Killed by Piccolo Daimo.
Killed when trying to kill Nappa.

Tien
Dies after wasting his last bits of energy to kill Nappa.

Chibi Trunks
Killed when Buu destroyed Planet Earth.

Zarbon
Killed by Vegeta.

Cell
Killed by Gohan.

King Cold
Killed by Future Trunks.

Yamcha
Killed by a Saibaman.
Killed when Buu destroyed Planet Earth.
Killed in the future.

Dabura
Turned into a cookie and eaten by Buu.

Grandpa Gohan
Killed when Goku turns Oozaru and stomps on him.

Dadoria
Killed by Vegeta.

Master Roshi
Killed when trying to seal Piccolo Daimo in a denshi jar.

Frieza
Killed by Trunks when he arrived on Earth.
Killed by Gohan when he came back from the dead.

Radditz
Killed by Piccolo's special beam cannon.

Majin Buu
Killed by Goku.

Shenron
Killed by Piccolo Daimo after he makes a wish.

Cell Jr's
All 7 killed by Gohan.

Babidi
Killed by Majin Buu.

King Vegeta
Killed by an Upper Cut from Freiza.

Yakon
Killed by Goku.

Pui Pui
Killed by Vegeta.

North Kaioshin
Killed by Majin Buu.

West Kaioshin
Killed by Majin Buu.

South Kaioshin
Absorbed by Majin Buu.

Dai Kaioshin
Absorbed by Majin Buu.

Rou Dai Kaioshin
Gives his life so Goku can live.

Arlians
Killed when Vegeta blows up the planet.

King Kai, Bubbles, and Gregory
Killed when Cell self-destructs.

Dende
Killed by Freiza.

Turles
Killed by Goku.

Slug
Killed by Goku.

Coola
Killed by Goku.

Bojack
Killed by Gohan.

Android 13
Killed by Goku.

Android 14
Killed by Trunks.

Android 15
Killed by Vegeta.

Paragus
Killed by Brolly.

Brolly
Killed by Goku, Gohan, and Goten.
The Bio Version was killed by water.

Janemba
Killed by Gogeta