Perhaps one of the biggest tropes of Dragon Ball, and by extension of anime in general, is a villain becoming a good guy. Despite killing people and destroying planets, a good chunk of the villains of Dragon Ball were given a second chance, mostly by Goku, who sees the good in everyone. Without Goku's kind heart, Vegeta would not have become the loving father and husband that he is today. The same goes for Piccolo, who Goku spared at the end of Dragon Ball, leading to the Namekian becoming one of his greatest allies and an influential mentor to his son.
This list of villains that became good guys goes on, and as is the nature of Dragon Ball, one starts to wonder just who among the former villains is the strongest. For this reason, we decided to rank them from weakest to strongest. Going all the way back to Dragon Ball, through Dragon Ball Z and into Dragon Ball Super, we gathered up every character that was once a bad guy at some point, but is now an ally, to find out which among them is the strongest.
15 THE PILAF GANG
Since the power level dials of the franchise didn't get cranked to 11 until Dragon Ball Z came around, the first few entries in this are gonna be pretty low tier. To start, we have the very first villains of Dragon Ball: Emperor Pilaf and his two henchmen, Mai and Shu. After being featured in the first saga of Dragon Ball and a few later sagas, we didn't see these three again until Dragon Ball Super, in which they had been turned to children with a wish from the dragon balls.
They also seemed to have given up their villainous ways, living comfortably on the Capsule Corp. premises and earning their keep as assistants to Bulma. The Pilaf Gang doesn't have much in the way of power, and even though they seem smart enough to build crazy robots, they definitely rank as the weakest former villains.
Next up we have one of the lesser villains of Dragon Ball, but he was an antagonist all the same. When Goku and Bulma arrived in Aru Village during the Pilaf saga, they found it was being terrorized by a great demon who stole the town's riches and women. This demon turned out to be Oolong, a pig who mastered the shifting technique and used it for personal gain. After Goku defeated him, Oolong eventually become a good guy.
However, Oolong didn't contribute much to the series in terms of combat, and though he was the one who stopped Pilaf from getting his wish (by interrupting and wishing for underwear), he's not really that strong. Oolong ranks just above the Pilaf gang since he's a master of the shape-shifting technique, which gives him some combat ability, but otherwise he's one of the weakest reformed bad guys.
13 THE OX KING
While the Ox King wasn't exactly much of a villain towards Goku and friends, he was known to be a frightening and violent king of fire mountain, one who attacked and threatened his way to wealth and power. But, those times are long passed, and after Goku married Chi-Chi, the Ox King worked hard to provide for and help his growing family, including building a house for the Son family next to Grandpa Gohan's original hut.
In terms of power, the Ox King isn't much to write home about, but he did train under Master Roshi, so he deserves some respect. His power level was too low to master the Kamehameha, but he was still a strong warrior when he was first introduced. The Ox King is also a massive human being, thus is incredibly physically strong. All that said, he's still small potatoes compared to other former villains.
Chiaotzu originally appeared alongside his best friend, Tien, as the first two characters shown with the power to fly. As such, since the flight technique requires ki, we are finally getting into the characters who have a somewhat measurable power level. Though he is not on the same level as some of the stronger characters in Dragon Ball, Chiaotzu is not without his strengths, including telekinetic abilities that most others do not possess.
Chiaotzu is able to move objects with his mind and communicate telepathically, both of which require intense concentration. With these powers, as well as his own ki-based abilities and strengths, Chiaotzu proved to be an asset to both Tien and the rest of the Z-fighters. However, as the franchise went on, his power paled in comparison to the likes of the Saiyans, thus his ranking gets knocked down quite a bit.
What's this? We ranked Yamcha as stronger than Chiaotzu? How could that be? He died from the Saibaman! First off, fans need to get over that memetic moment, and second, Yamcha isn't actually weak. He might not be the strongest human being in the series, but Yamcha still has a heck of a lot of determination and a good amount of power to back it up. But, this mullet-headed martial artist didn't always use his skills for good.
Way back in the early days of Dragon Ball, Yamcha was kind of a jerk. Well, not "kind of," more like "definitely." Seriously, the guy made his living off of beating people up for their belongings in the desert. Eventually, he gained a conscience and started fighting for good, actually proving his worth as a strong and capable warrior in the later days of Dragon Ball and the early days of Dragon Ball Z.
Fans often agree that Krillin is the strongest human fighter in the entire Dragon Ball franchise, and we're inclined to agree with them. However, a close second is definitely Tien, who was introduced to the series as an antagonist, doing the bidding of his deplorable martial arts master. He also served as an opponent in the 22nd World Martial Arts Tournament, not exactly a villain in the purest sense of the word, but he definitely wasn't a good guy from the start.
But, like many a Dragon Ball villain, Tien Shinhan soon became friends with Goku and company and joined the ranks of the Z-fighters. In terms of strength, Tien's power is nothing to scoff at, and though he his human (though perhaps with some alien heritage?) he has shown to hold his own against the likes of Saiyans and the androids, making him the strongest human on this list.
9 ANDROID 17
Androids 17 and 18 were built with the intention of destroying Goku as revenge for the fallen Red Ribbon Army. In both timelines that the two wreaked havoc in, they never really got the chance to do this, since Goku fell victim to a heart virus. Regardless, Android 17, along with his sister, still destroyed cities and attacked people with no concern for who they hurt or killed.
These days, Android 17 has renounced his evil ways and works as a park ranger while caring for his family. It is his great power that makes him both a strong warrior and an effective protector of wildlife, as Android 17 has an infinite power source within him that prevents him from running out of energy and/stamina, and though the level of his strength has a limit, he is still a force to be reckoned with.
8 ANDROID 18
Like her brother, Android 18 was first introduced as a villain so horrible, Future Trunks had no other choice but to go back in time and prevent her from causing an apocalyptic future. Android 18 showed little empathy towards others and was happy to attack cities with her brother. Fast forward a bit, and she is now happily married to Krillin, whom she had a daughter with.
The power difference between Androids 17 and 18 is somewhat hard to pin down, but there is some evidence that points toward 18 being stronger than her brother. It was stated that Android 17 initially had a flaw in his systems that prevented him from accessing the full potential of his power, which leads us to believe that the technology used to convert him to a cyborg was inferior to that used in his sister, thus leading to 18 ranking slightly higher.
7 ANDROID 16
Android 16 was never cut out for villainy, despite being built with the intention of getting revenge on Goku for his creator, Dr. Gero. Since Dr. Gero based his likeness on that of his son, who died in the line of fire, he couldn't bear to watch his son die a second time. Thus, Dr. Gero programmed Android 16 to be a kind-hearted and gentle person. As such, 16 was quick to fight alongside the Z-fighters in the Cell games.
Despite his gentle nature, Android 16 is still incredibly strong. He's got an internal power source that gives him infinite energy and unlimited stamina and it it is also stated that Android 16 is the strongest of the Red Ribbon Army androids, second only to Cell, putting him just above his fellow Androids.
When Piccolo was first introduced, he was known as Piccolo Jr., the son of King Piccolo whom Goku had defeated and killed at the World Martial Arts Tournament. Piccolo Jr. had all of his father's memories and was out to get revenge on Goku. However, after being defeated and spared by Goku, Piccolo eventually became an ally, helping to defend against the Saiyans and training Gohan to fight while Goku was dead.
Piccolo's power is perhaps the most dynamic on this list, by which we mean he has reached great levels of strength, only to get even stronger later on. Piccolo has the power of both a warrior-type Namekian, achieving the power of a Super-Namekian, as well as the magical abilities of the dragon clan, due to his origins as being part of Kami. Put this all together and Piccolo is easily one of the strongest ex-villains in the series.
5 MAJIN BUU
Majin Buu was an ancient evil demon with such immense power that even the Supreme Kai feared him. Yes, the god who stands above the lower gods of the universe was afraid of a mortal being, now that says something about just how powerful Majin Buu really was. After a long battle, Kid Buu, the original form of the evil creature, was defeated, and his jovial, light-hearted self was spared by Goku at Mr. Satan's request.
This Buu, often dubbed "Fat Buu" or "Good Buu," found a place in society after the dragon balls were used to wish away the memories of his past actions. With the guidance and help of Mr. Satan, Buu joined the ranks of ex-villains amongst Goku's friends and allies, and though his power was not quite the same as his complete self, he still ranks as one of the top five strongest ex-villains.
We know what you might be thinking, "Frieza was never a good guy!" While this is technically true, in the Universal Survival saga of Dragon Ball Super, Frieza has joined Universe 7's team in the Tournament of Power. While this wasn't exactly done with the greatest intentions, Frieza is still considered an ally at this point, so we're going to give him a temporary "ex-villain" status.
In terms of power, Frieza is a cut above the rest. Gifted with natural strength and several transformations that make him even stronger, Freiza used his incredible power to form a galactic empire by way of his iron fist. Fast forward to Super, and Frieza trained for the first time in his life to gain his Golden form, which makes him stronger than even Super Saiyan Blue, though only for a small amount of time.
At last we come to the fan favorite ex-villain, the prince of Saiyans himself, Vegeta. Vegeta's character development is easily one of the most interesting in all of pop culture; he started as a psychopathic murderer who killed for the sake of showing his strength and power, but he eventually came to be a caring and loving person, one with a family that he fights to protect. Talk about redemption arcs!
Just as Vegeta is the most beloved villain-turned-good-guy, he is also one of the strongest. Right from the get-go, it was clear that the prince of all Saiyans was incredibly strong, as it took the help of Goku and his friends to take him down. Throughout the rest of the franchise, Vegeta became a Super Saiyan, a Super Saiyan 2, and a Super Saiyan Blue 2, all by way of his own grit and determination to get stronger.
This one might be the most surprising and confusing entry on the list, but don't worry, we'll explain. You might be wondering when Goku could have ever been considered a villain, and the answer goes back to before the events of the original Dragon Ball. When Goku was sent to Earth as a baby, he was meant to destroy and/or conquer it, something his Saiyan instincts were supposed to drive him towards.
This is enough to consider him a villain, and were it not for a head injury as a baby — which replaced his rebellious personality with a calmer, gentler one — he would have most likely gone through with his mission. Thus, since he ended up being the protector of Earth, Goku is, in many ways, the first ex-villain of the franchise, and since he is definitely one of the strongest characters, he ranks as number two on our list.
At last we come to one of the most recent ex-antagonists of the franchise, Lord Beerus. Beerus might not be a truly evil villain by most standards, but he definitely came close to destroying the Earth for petty reasons. Regardless, as soon as Goku and friends learned that his destructive tendencies could be quelled with good food, Beerus became yet another ex-villain in the Dragon Ball franchise.
Beerus ranks as the number one amongst the former villains by the the fact that he is a god that possesses both godly ki and the power of destruction. When Goku also had the power godly ki, Beerus was able to hold is own using only 70% of his power, and even this was enough to cause their clash to shake the very fabric of the universe. Without a doubt, Beerus is the strongest ex-villain in the world of Dragon Ball.