The Saiyan arc marks a major shift for Dragon Ball. In just a single chapter, Raditz arrives on Earth and fundamentally changes the franchise. Where there once an overt martial arts aesthetic to the series, Toriyama opts for something more akin to science fiction. Characters still fight and martial arts plays an important thematic role, but things undeniably change.
The Saiyan arc also brings with it a higher scale of power. Raditz is a foe so imposing that Goku is forced to give his life just to defeat him. This is an arc that begins with the heroes hopelessly outclassed but ends with Goku giving Vegeta the fight of a lifetime.
Yamcha’s in the top ten here more thanks to technicalities than his own genuine talent. Toriyama never really focused much on Yamcha, even as early as the 21st Tenkaichi Budokai, but he was always present. He didn’t always contribute, but Yamcha was a reliable character for tournament settings.
Naturally, this means he’s able to keep up without falling too far behind. Tragically, this is the last time he’s one of the series’ strongest characters as he never quite recovers from his death in the way other characters do. Yamcha’s a little bit stronger than the average Saibaiman and while he technically wins, it costs him his life & status as a main character.
Raditz may round down the bottom of the strongest characters hierarchy for the Saiyan arc, but he gives the main characters the single hardest fight in the entire arc. Goku and Piccolo go into the fight more or less knowing they can’t win head-on and that any victory would be nothing short of a miracle.
Raditz is so much faster and so much stronger than anything that came before. Dragon Ball being Dragon Ball, however, it doesn’t take long for the supporting cast to all surpass Raditz (or most of them, at least). After training with Kami, Kuririn and Tenshinhan are both strong enough to defeat Raditz.
For someone who spent the entire Piccolo Daimao arc dead and seemingly didn’t train much after the 23rd Tenkaichi Budokai (but it seems like barely anyone did), Kuririn manages to power up quite a bit leading up to the fight with the Saiyans. In less than a year, he’s stronger than a character he swore would kill him.
Not just that, Kuririn nearly kills Nappa with his Kienzan. Throughout the fight with the Saiyans, it’s Kuririn who devices the most plans, actively contributing to Vegeta’s ultimate defeat. Kuririn is a good example of why raw power doesn’t matter in Dragon Ball. Even though he’s on the weaker end, he’s still a serious threat.
Tenshinhan is even stronger than Kuririn once the Saiyans finally arrived, but he, unfortunately, doesn’t get the chance to show off that strength as he ends up dying shockingly early— after spending three arcs in a row as the closest thing the series had to a deuteragonist. Kuririn ends up taking more prominence, and that’s pretty it for Tenshinhan.
Which is a bit strange since he really is strong when the Saiyans arrive. As Kuririn had already died once, though, Tenshinhan was the only character who could realistically die alongside Chaozu and Yamcha at the time. It also just helps put into perspective just how strong Nappa was. Before this fight, Tenshinhan was in the top three alongside Goku and Piccolo.
Speaking of Piccolo, it’s actually surprising how weak he is all things considered. Everything in the arc paints him as an incredibly strong and skilled martial artist (and he is,) but his Battle Power never exceeds Nappa’s— which is already low compared to Vegeta. Battle Power’s bogus, though.
It also has no real bearing on Piccolo’s Battle Power. Above the Earthlings, everyone just falls right where they need to be. Piccolo’s incredibly strong, but training with Gohan may have slowed him down, keeping him from getting any stronger. Either way, the Namek arc ends up giving Piccolo such a boost in power that it hardly ends up mattering.
Kaio needs to be strong enough to train Piccolo at the start of the Namek arc while also being weaker than Nappa. Considering the gap between Piccolo and Nappa isn’t that big, Piccolo might have already close to Kaio in terms of Battle Power by the time he arrived in the afterlife to train.
It’s interesting that Kaio notes at all that he’d be no match for either Saiyan. He’s the strongest divine figure in the series up to that point and Toriyama just straight up removes him from the equation as a genuine threat. This is a trend that the rest of the franchise followed comfortably up until Battle of Gods.
The characters specifically end up blaming Vegeta (likely because he survives,) but Nappa is responsible for Chaozu’s, Tenshinhan’s, and Piccolo’s direct deaths while also being related to Yamcha’s death. He’s strong enough that he could have taken out both Kuririn and Gohan had Goku not arrived in time.
It’s rare that Dragon Ball shows one character taking out so many members of the main cast. Goku is literally the only person out of six to be able to hold his own against Nappa. That said, both Kuririn and Piccolo manage to do some serious damage on him, to the point where Gohan could have potentially defeated him early.
3 Son Gohan
Gohan’s an interesting character in the Saiyan arc. On one hand, his base Battle Power seems to be lower than just about everyone's. It makes sense, he’s a kid after all. When enraged, though, Gohan displays an insane amount of power. Early on, it’s enough to push him beyond what Goku’s capable of.
Gohan’s rage is also enough to allow him to fight toe to toe against Vegeta. It’s ultimately Gohan who gets the arc’s final fight, not Goku. By that point, though, Goku had worn Vegeta down considerably and the Prince of all Saiyans was no longer fighting at full force, whereas Gohan had eaten half a Senzu inbetween fighting Nappa & Vegeta.
2 Son Goku
Goku begins the arc barely strong enough to take on Raditz and he ends up by driving Vegeta off of Earth through sheer force of will. The Kaioken ends up becoming Goku’s most valuable tool in the Saiyan arc, pushing his body to extreme lengths in the pursuit of the strength possible to fight off the Saiyans.
Through the Kaioken, Goku is actually able to become significantly stronger than Vegeta. It isn’t enough to kill him, but it’s enough to push Vegeta to transform into an Oozaru. With a 4x Kaioken, Goku’s Kamehameha nearly obliterates Vegeta— beginning one of the most important rivalries in manga history.
There’s just no getting around how freakishly strong Vegeta is in this arc. Even without his Oozaru transformation, Goku has to basically kill himself just to stand a chance against Vegeta. Vegeta kills Nappa effortlessly and it takes literally every single surviving martial artist working together to take out Vegeta.
As an Oozaru, he gives Goku a beatdown the likes of which he never sees again. Goku is truly manhandled. Even at death’s door, Vegeta nearly manages to defeat everyone else who challenges him. Gohan, Kuririn, and Yajirobe have to progressively chip away at Vegeta just to subdue him.