When Goku finally arrived at Namek, his power was much higher then when he first left for the trip and he easily defeats the elite team called the Ginu force. After he learned what was going on at Namek, he meets the captain of the Ginu squad, Captain Ginu. During their battle, Ginu realizes he is no match for Goku and steals his body. Goku is able to get his body back by tricking Ginu and traps him in the body of a frog. Goku is again severely injured and has to be put in a healing chamber. As soon as he gets out of the healing tank he battles one of his worst enemies, Freeza. After an intense battle, he realizes he is no match for Freeza and uses his trump card? the Genki Dama (spirit Bomb). They all think he is defeated, but they soon find out that he isn't when Freeza kills Krillin. Goku gets so enraged, he turns into a Super Saiya-jin. In the end, Goku defeat's Freeza and barely escapes Planet Namek before it explodes.
Goku was thrown through space and landed on a far away planet called Yardratt. It is there were he learned the Instantaneous Movement technique. Goku eventually came back to earth, and when he does, he meets Future Trunks. That is when he learns Trunks story and about the androids that will arrive in three years. Goku trains hard, and when the androids arrive, he gets the heart attack that F. Trunks told him about. He uses the medicine Trunks gave him and is eventually healed, but by that time there was a new threat? Cell. Goku decides to go into the room of spirit and time and train with Gohan. Under Goku's training, he eventually reaches the SSJ level. When they leave, they rest for a few days before the Cell games.
When the game starts, Goku fights Cell but gives up. He knew that his son Gohan would be strong enough to defeat him and has him challenge Cell. But before Gohan ends up defeating Cell, Goku again sacrifices his life to save the earth. He aids Gohan from heaven and guides him to defeat Cell.
Goku chooses to stay in heaven and competes in the heaven tournament where he comes to a stalemate with another warrior called Pikhan. While in heaven, Goku achieves the SSJ2 level and the SSJ 3 level. Goku is able to come back to earth for a shot time, and while he was there, he met his second son Goten and entered in the Tenkaichi Budoukai Tournament. While in the tournament he notices strange things happening. Later on, he ends up fighting Majin Vegeta. They both were equal in strength at the SSJ 2 level, but Vegeta ended up winning by cheating and knocks Goku out while he wasn't looking.
While Goku was on earth, he was able to fight fat Buu and show off his SSJ 3 form. He didn't want to beat him; all he was doing was giving Trunks enough time to retrieve the Dragonball radar. Before Goku went back to heaven, he taught Goten and Trunks how to do the fusion dance.
While in heaven, Goku watched over what was going on with Buu and the others. During Gohan's fight with Buu, Dai-Kaioshin decides to give his life to Goku so he can go back to earth and fuse with Gohan using the potara earrings. When Goku teleports back to earth, Gohan ends up getting absorbed by Buu so Goku fuses with Vegeta instead. They both form into Vegitto and do battle with Buu. Vegitto is purposely absorbed by Buu so he can rescue everyone who was absorbed by him. The permanent fusion with Vegeta was canceled out when they were absorbed. While they were inside Buu, Goku and Vegeta rescued Gohan, Piccolo, Goten, and Trunks and in the process saved fat Buu (they don't take Fat Buu with them, but Buu spits him out later on). They all escape through one of Buu's blowholes and magically turn back to their normal size. When they removed Fat Buu, something started to happen to Buu. He turned back to his original form and when Goku and Vegeta challenged him, he destroyed the earth. Kaioshin was able to save Goku, Vegeta, Mr. Satan, and his puppy before the earth was blow away.
They were all transported back to heaven. While they were there, Buu went from planet to planet destroying them one by one killing all life that inhabited it. Goku and Vegeta decide to max their power so Buu would come to them and stop killing innocent people. Buu arrives and Goku is the first to fight. Goku battles hard, but his power starts to run low and he starts to loose. When Vegeta tries to fight him, he sees that he is no match for Buu. Goku saves Vegeta and continues to fight Buu. Then, Mr. Satan interferes with the fight and it is learned that Buu can't seem to harm Satan. Buu solves this problem by spitting out fat Buu (fat Buu was making it so Buu couldn't harm his friend, Mr Satan). Buu starts to fight fat Buu giving Vegeta and Goku a chance to devise a plan.
Vegeta comes up with the plan to use the Dragonball's to revive on earth, and all the people who were killed by Buu. His plan was for Goku to use a huge Genki Dama from the energy gathered from the people of earth and destroy Buu. After the wishes were made, Goku started to gather the energy to make the huge Genki Dama, but he was having a hard time convincing the people on earth to give up their energy. But when Mr. Satan asked everyone to raise their hands and give their energy, they did because they trusted him. After the energy was collected, Goku released the Genki Dama straight at Buu. But Goku's energy was low and he couldn't destroy Buu with it. As Buu started to push the Genki Dama back at Goku, Dende used the last wish from the Dragonball's and asked for Goku's strength to be returned. After he was healed, Goku easily destroyed Buu. Right before Buu's death, Goku wished that he would come back as a good guy so he could see who was really stronger.
Ten years later, Goku entered another Tenkaichi Budoukai tournament and tells everyone he has been watching someone with a great power. When they picked the numbers to see who would battle who, Goku had fat Buu rig the numbers so Goku would fight a young boy names Ubuu. Later on it is found out that Ubuu is actually the reincarnated Buu. In the middle of the tournament after he fought Ubuu, Goku leaves to train him
In Dragonball GT, Goku is turned into a child and goes on an adventure to find the black star Dragonball's with Trunks, and his granddaughter Pan. Once they return from their adventure, they find out that Bebi has been on a rampage while they were gone. Goku ends up reaching the SSJ 4 form and defeats Bebi. After his fight with Bebi, he meets up with some of his old enemy's, Dr. Gero and Android 17. Dr. Mu Creates another 17 and the two 17's fuse becoming Super 17. With the help of 18, Goku defeats 17 with a dragon punch.
Shortly after, Goku finds out that the Dragonball are starting to crack. Seven evil Shenlong's appear and Goku and his crew fight them one by one. In the end, Goku absorbs the Dragonball's and flies off on the eternal Dragon.
Techniques
Bukujutsu: The ability to fly with one's ki.
Fusion: This technique is used to fuse two people into a single person, and give the fused person a huge power boost. Anyone can do the Fusion, but you have the same power as whoever you fuse with, and you must learn the correct pose and form. It's easy to make a mistake and fuse into something far weaker though. The Fusion lasts for 30 minutes before the fused person becomes two again.
Genki Dama: A large ball of energy gathered from nature, humans, etc., which lend you their energy.
Shunkanido: The user places two fingers on his forehead, searches for a Ki he wants to go to, then when he finds it, can teleport there.
Jan-Ken Punch: A Japanese game identical to that of "Rock, Paper, Scissors." Goku then has three different types of Jan-Ken Punches.
Kaioken: This is primarily a power-up move. When Goku uses this technique, he flares up and gains a large boost to his speed and power. Goku can also use multiplied power to his Kaioken.
Kamehameha: It is a Ki blast, which to start is charged up held behind the firer in cupped hands, then brought forward to release a large blast of energy
Kiaiho: An invisible force attack that knocks one's opponent back. It can be shot either from an open palm or from the eyes.
Kienzan: It is a flat, disc-shaped Ki blast, which can be used to slice through its target with deadly accuracy.
Zanzoken: The user can move so fast he leaves an after-image, while attacking from another standpoint.
Little known facts
Goku's real name is Kakarroto. Goku was a name given to him by his adopted father, Grandpa Gohan.
Goku's real father is Bardock. He died when he tried to save the planet Vegeta from Freeza.
Goku never met his son Goten until long after he was born.
Goku's full name is Son Goku. His last name, Son is put at the front instead of the back.