Dragon Ball has the tools it needs to upgrade the anime’s weaker Z-Warriors through King Kai and the Kaio-ken technique. For too long, characters like Krillin, Tien, and Yamcha have lagged far behind the show’s Saiyan heroes.
As time passes, the gap between the top two Z-Warriors and everyone else keeps getting bigger and bigger. Though their power levels saw some significant gains over the course of the Saiyan, Frieza, and Cell Sagas, none of the three characters have been able to make a difference against a main villain. In fact, they typically don’t even get chances to take part in the fighting anymore. In the Tournament of Power, Krillin and Tien became the first Universe 7 team members to be eliminated from the Tournament of Power, and Yamcha wasn’t even strong enough to warrant an invitation. Admittedly, Gohan and Piccolo are a long way away from Goku and Vegeta as well, but Dragon Ball Super is at least taking meaningful steps toward making them stronger.
Piccolo and Gohan aren’t the only Z-Warriors who need this treatment, as Tien, Yamcha, and Krillin have all lost their relevancy. Of course, what they can accomplish is limited because of biology and the fact that they’re Earthlings, but Dragon Ball already has a way of sidestepping this obstacle. All three of the characters could stand to benefit greatly from the Kaio-ken technique, which is capable of multiplying a fighter’s strength, speed, and senses by several degrees. By utilizing one of Goku’s most popular moves, the trio could experience significant power boosts.
The three learning this skill is possible in the Dragon Ball anime. The show had a chance to impart this ability to Tien and Yamcha when they became pupils of King Kai, the same person who originally taught it to Goku. However, neither were shown practicing it. Their power levels shouldn’t have been an issue, since King Kai confirmed that both exceeded the strength Goku had when he left the planet to fight Vegeta and Nappa in the Saiyan Saga. And since Krillin's strength level is near or above them in power, he too has what it takes to pull it off. Unfortunately, it may be too late for Chiaotzu to ever regain his relevancy, but the other three should be able to make some serious progress if they finally learned the Kaio-ken technique. As for how they could acquire it, they could either pay another visit to King Kai or convince Goku to teach it to them.
The Dragon Ball video games often give them the Kaio-ken technique to compensate for their inability to transform. This approach makes sense because it’s one state that the three Z-Warriors could enter if they only knew how. Letting the characters learn Kaio-ken wouldn’t completely fix their problems, but it would serve as a way forward, which is what they need to make a real difference in the battle against the villains that threaten the Earth.