Android 20:
Otherwise known as Dr. Gero, he is they creator of all the androids. He first appeared with #19 in a city. There he injured Yamcha by shoving his hand right through his body. Then he flew to some fighting grounds and watched #19 get defeated by super saiyan Vegeta. After that he fought with Piccolo but got his arm right arm chopped off and his ass kicked. So he flew away and released #17 and #18. But #17 and #18 killed him.
Other Spellings/Name: Dr. Gero
Death(s): Killed by #17

Android 19:
Even though this guy is powerful, he looks like a fat impersonation of Chaozu. He went with #20 to a city and basically destroyed it. Then he flew to some kind of battle ground. He fought with super saiyan Goku and wasn't doing too bad, then luckily for him Goku had a heart attack and Yamcha flew him home to recieve treatment. Then he fought against super saiyan Vegeta (1st time ssjvegeta) and died.
Death(s): Killed by Super Saiyan Vejita with the Big Bang Attack

Android 18:
She was realeased by Dr. Gero along with her brother #17. She and her brother killed Dr. Gero. She fought against Vegeta and the earth warriors but in the end she sided with them when Cell arose. Krillin wished a self-destruct bomb in her head away and after that she married Krillin. They had a daughter named Marron.
Japanese Name: Juuhachi-Gou
Death(s): None. But she got absorbed by Cell.

Android 17:
The brother of #18, they killed Dr. Gero. He looks exactly like #18 only he is a boy and he has black hair with a red bandanna hung around his neck. He too fought the Z warriors. He ended up getting absorbed by Cell which was half of what Cell needed to become Perfect Cell.
Death(s): Killed/absorbed by Cell(wished back to life by Krillin)

Android 16:
This android was programmed to kill Goku too. But when Cell arose, he fought alongside the z fighters. He fought in the cell game but was absorbed by Cell and that was the last anyone ever heard of him.
Death(s): Killed by Cell

Bardock:
Goku's dad. He was a low rank soldier in the saiyan army but was killed when Freeza destroyed Planet Vegeta. He invented the Artificial Moon that could turn any saiyan with a tail into a oozaru(were-monkey). He isn't heard of much in dbz.
Death(s): Killed by Frieza

Bee:
This is Mr. Satan's dog. Don't really know much about him but I do know that Mr. Buu is really close to him and when someone killed Bee, Mr. Buu goes whack and separates himself into Good and Bad Buu.
Death(s): Killed by a sniper

Bulma:
She was an original character of dragonball. She goes with Gohan and Krillin to planet namek to get a wish from the namekian dragonballs. She ends up being a pain in the neck always screaming and ordering Gohan and Krillin around. She ends up marrying Vegeta and having a son with him called Trunks.
Japanese Name: Buruma
Death(s): None

Burter:
He is a member of the Ginyu Force. He is blue with a lizardlike voice and face. He is really fast. He watched Guldo die at the hands of Vegeta, Gohan, and Krillin. And watched alongside Jace as Goku killed Racoom. He and Jace tried to battle but were unsuccessful. Goku koed him easily and then Vegeta finished him off.
Japanese Name: Baata
Death(s): Defeated by Goku, killed by Vejita

Buu:
Buu is a mystical being. He was sealed up long ago where he could not escape. Someone with alot of energy could let him out, but there was no such person. So Babidi and Bibidi stole energy from many people, Gohan and Vegeta included. And when they had enough energy, they released Buu. Buu caused havoc on earth and fought the Z fighters. He defeated everyone except Goku. But Goku could not defeat Buu himself so Vegeta was granted life to help Goku out. So while Vegeta distracted Buu in fighting, Goku gathered a super super spirit bomb and nailed Buu with it, Buu was killed. After his death, Buu is reincarnated to become Ubuu or rather Mr. Buu, who was a good person and was good friends with Mr. Satan.
Death(s): Killed by Goku's super spirit bomb with the help of Vejita(and Mr. Satan)

Cell:
Cell is an Android that was made by Dr. Gero. He was made from the cells of the Z warriors. He was quite a challenge. He came to earth and fought the androids and the Z warriors. He managed to absorb #17 and #18 which made him into Perfect Cell, who was more powerful and better looking. Then he fought the Z warriors and defeated all the fighters when he released his Cell Jr.s, who were mini replica's of himself, or rather his babies. Gohan was the only one that survived the onslaught. After seeing Trunks died, that was too much for Gohan and he turned SSJ2 and killed Cell for good.
Japanese Name: Seru(I think)
Death(s): Killed by Super Saiyan 2 Gohan's Kamehameha

Chaozu:
Chao-zu is a small white dwarf who is the companion of Tenshinhan. He looks like a porsalin doll, he was the second to die in the fight against Napa. He can talk with Tien telepathically and is pretty strong for a small guy like himself.
Other Spellings: Chaotzu
Death(s): Self-destructed on Napa

Chichi:
Goku's wife. She is always worried about Gohan's wellbeing. She always wants him to study instead of fighting like his dad. She asked Goku if he would marry her and because Goku didn't understand, he thought Chichi was going to make him dinner and agreed.
Death(s): None

Dedoria:
Another one of Freeza's top henchmen. He is pink and pudgy and looks like a big pink blowfish. He killed 3 nameks really easy and nearly got to Krillin, Gohan, and Dende. But he died at the hands of Vegeta.
Other Spellings: Dodoria
Death(s): Killed by Vejita

Dende:
A young namek who is rescued by Krillin and Gohan. He leads them to Guru so they can get a dragonball and awaken their hidden powers. He also became the next Kame-Samma after the previous kami merged with piccolo. He was given the power to heal by Guru.
Death(s): Killed by Frieza

Freeza:
A very very powerful enemy of Goku & Vegeta. He plans to find all the seven dragonballs on the planet namek and become the most powerful person in the universe. He has 4 forms that allow him to grow stronger. He was killed by Goku for the first time after Goku turned Super Saiyen for the first time. But then, his father found him floating in space and reconstructed him to become half android. He returned to earth to take revenge but was killed by Future Trunks who had come from the future to save Goku from a heart desease.
Other Spellings: Frieza, Freiza
Death(s): "Killed" by Goku on Namek. Came back as a half-android and was killed by Super Saiyan Trunks.

Garlick Junior:
Garlick Jr. is a little green guy that looks like a namek. His father came to earth a long time ago wanting to be Kami, but he was denied it. So Garlick Jr. wanted some revenge and attacked Kami's lookout. He and his henchmen got control of Kami's lookout and made nearly every person on earth evil. But thanks to Gohan, Krillin, and Piccolo, he got sealed in the deadzone for eternity.
Death(s): Never really killed, but got sucked into the deadzone twice.

Ginyu:
The leader of the Ginyu Force and the most powerful. He has the ability to switch bodies with people. He injured himself by punching a hole in his chest and then he changed bodies with Goku. but when he tried it again, he changed bodies with a frog and was squashed.
Other Spellings: Ginew
Death(s): No deaths, but in the end became a frog.

Gogeta:
Pronounced as Gojita, Gogeta is a fused being, meaning he is formed when two fighters form together to become one. Gogeta is the fusion character of Goku and Vegeta hence the name Gogeta. The fusion only lasts for 30 mins since it does not use pottari earings.
Other Spellings: Gojita
Death(s): None

Gohan:
Gohan is the first son of Goku and Chichi. He is half-saiyan and the brother of Goten. He showed early signs of great power at the age of 5 when he headbutted Raditz in the chest and broke his armor, his power level was around 1200. After his dad died in that battle, Piccolo trained him in the wilderness because they found out that 2 powerful saiyans would be arriving in a year. He didn't make much of a difference in that fight cause he chickened out a couple of times. Piccolo saved Gohan's life by sacrifycing his own and started a long friendship. He then traveled to namek with Krillin and Bulma so they could get the namekian dragonballs and wish his new friend Piccolo back to life. There he got his hidden powers awakened by the eldest namek, Guru. His power level increased alot. He fought Guldo and the Ginyu Force and showed great courage. He fought against Freeza and showed gave them some hope of beating him. But freeza beat him down. Thanks to Dende's healing power, he got back full health. He also managed to save Piccolo's life once in the android saga against #20. He goes on to becoming the Saiyan Man and starts saving people (somewhat like superman) but he blows his cover when he turns super saiyan. He also killed Cell and Cell Jr.s when he became the first to turn Super Saiyan 2.
Other Spellings/Names: Son Gohan
Death(s): Killed by #17 in the alternate timeline.

Goku:
Goku is a saiyan from Planet Vegeta. His saiyan name is Kakarot. He was sent to earth to destroy it. He was found in his space pod by Grandpa Gohan(not to be confused with his son). He was a crazy kid as all saiyans are. But after suffering a head injury falling down a ravine, he became purely good. He acidentally killed Grandpa Gohan when he went oozaru. He met up with Bulma and they became good friends. In dbz, his first fight is with his own brother, Raditz. He ends up sacrificing his life so Raditz can be killed which both of them die by Piccolo's special beam cannon. After dying, he traveled snakeway and trained with King Kai, increasing his powerlevel and learning the kaioken attack along with the spirit bomb. Then he was wished back to life and he fought Napa. He killed Napa easily. Then he fought Vegeta and thanks to the help of Gohan, Krillin, and probably Yajerobi, he defeated Vegeta. Then he traveled to namek and fought the Ginyu Force. He suffered serious injuries in defeating the Ginyu Force so Vegeta put him in a healing tank and he got healed. Then he fought Freeza and after seeing his best friend Krillin die, that was the last button Freeza had pushed. He turned Super Saiyan and whooped Freeza. In the beginning of the android saga, he fights #19 but gets a heart attack so he is taken home. I don't know much yet cause I haven't seen that far. But in the Buu Saga, he makes a super spirit bomb and killed the all powerful Majin Buu.
Other Spellings: Gokou, Gokuu, Son Goku/Gokou/Gokuu
Death(s): Killed by Piccolo's makensappou in the fight against Raditz. Killed by Cell when Cell self-destructed.

Goten:
This is Goku's second son. He is best friends with Chibi Trunks. He learned to go Super Saiyan at an early age(around 7years old). He gets in alot of trouble because of Chibi Trunks who is a trouble maker thanks to his fathers genes. He first appeared in the Buu saga, Gohan trained him how to fly and fight. He can fuse with Trunks to become Gotenks.
Death(s): None

Gotenks:
Gotenks is a fused being, meaning he appears when two people fuse/join to become 1 person. He is made of Goten and Chibi Trunks. He is a powerful fighter being the only person other than Goku to turn Super Saiyan 3. But he is cocky and usually gets his ass kicked because he under estimates his opponents.
Death(s): None, but got absorbed by Buu.

Guldo:
A member of the Ginyu Force. Guldo is a fat and short frog-faced guy with four eyes. He is the weakest of them all. He has the ability to stop time for instants of time which helps him out. He battled the enraged Gohan and Krillin and was losing really bad. But then he got them caught in a mind freeza and that helped him out. He was about to finish Gohan and Krillin off when Vegeta shot a finger laser at him then finished him off.
Japanese Name: Gurudo, Guld
Death(s): Head decapitated by Vejita, then blown to smitherines by Vejita.

Guru:
This is the eldest Namek. He was the last surviving namek after all the other ones died. He is the father of all the current Nameks(except for Piccolo). He created the Namekian dragonballs which can grant you 3 wishes. He is guarded by Nail, the most powerful Namek next to Piccolo. He awakened Gohan's and Krillin's hidden powers and also gave Dende the power to heal.
Japanese Name: Saichohroh
Death(s): Died of old age.