Since transforming into a Super Saiyan during his fight with Frieza on Planet Namek, Goku has indefinitely pushed the limits of Saiyan strength. He's pioneered numerous new forms and has been able to overcome some of the strongest opponents in all of the 12 universes. While the face of Dragon Ball is undoubtedly the most strong Saiyan though, he is far from the only one.
As well as the Saiyans who are currently living on earth, many more exist in different timelines, galaxies, and universes. Some, like Broly and Future Trunks have been around for decades now, but most of them were added to the series fairly recently. Dragon Ball Super and Dragon Ball Heroes have each introduced their fair share; as have the many Dragon Ball movies. They might not be quite up to Goku's incredibly high standards, but they are immensely powerful nonetheless.
10. Yamoshi
Though a lot of fans probably won't know Yamoshi by his true name, they should be fairly familiar with his title. Yamoshi is the Legendary Super Saiyan to whom both Frieza and Vegeta are constantly referring prior to Goku first becoming a Super Saiyan on Namek. Given that he died more than a thousand years prior to the events depicted in both the manga and the anime, it's difficult to gauge his true power levels, though it seems somewhat safe to assume that they were pretty high.
Initially, Vegeta implies that Yamoshi was only able to transform into a Super Saiyan while in his great ape form, but this has never been officially confirmed. Later on, in Dragon Ball Super, it is revealed that Yamoshi's spirit played an integral role in the creation of the Super Saiyan God transformation. It's again unclear as to whether Yamoshi was able to achieve the form himself, but his knowledge of it would at the very least seem to suggest that he had reached a level beyond regular Super Saiyan prior to his death.
9. Future Trunks
As most Dragon Ball fans know, Future Trunks is a recurring character who first appeared in the Android Saga. He comes from an alternate timeline where Goku died of a heart virus, and Androids 17 & 18 managed to decimate the world. While Future Trunks never unleashed his true power in Dragon Ball Z, as he was arguably the weakest of all the Saiyans during the time he was introduced, his return to prominence in Dragon Ball Super made sure he could face the universe's biggest threats. Though Trunks' infamous Super Saiyan Rage form is often disregarded as a contrived one-off transformation, it nonetheless granted him the ability to spar with characters who were far beyond the level of power it took to tear open holes in dimensions and potentially threaten the fabric of the universe.
8. Cabba
Cabba is one of the three Universe 6 Saiyans who were introduced in Dragon Ball Super; all of whom are named after vegetables. He might not look it, but this skinny little Saiyan is incredibly strong and is also a very fast learner to boot. He masters the Super Saiyan transformation with very little tutelage and holds off some strong competition during the tournament of power while in this form.
For whatever reason, Vegeta has taken a real shine to Cabba and agreed to train the young Saiyan following their battle on the nameless planet. With such an accomplished mentor now in his corner, it's quite possible that Cabba will become much stronger in future arcs and, at the very least, rival some of the other Saiyans from Universe 6.
7. Caulifla
Caulifla is a much more accomplished fighter than Cabba and is able to progress from Super Saiyan 1 to Super Saiyan 2 almost immediately. After Goku helps her to master the second form during the tournament of power, she becomes even more powerful, although still has some way to go if she hopes to challenge the very best.
Even at her strongest, she's nowhere near a match for Goku who seems to be toying with her for much of their battle. Although he does transform into Super Saiyan form to deflect a powerful attack, he spends most of the fight powered down which suggests that he could defeat her quite easily if he so wished. She does provide more of a challenge once fused together with Kale, although even then is unable to defeat Goku.
6. Kale
Kale is undeniably the strongest Saiyan from Universe 6. Her latent power is through the roof and she was designed to mirror the infamous Broly. Her power is said to rise continuously when in her berserker state, and she was strong enough to ignore a Super Kamehameha from Super Saiyan Blue Goku. Kale's rampaging power was so great in Dragon Ball Super it even drew attention from Jiren. Kale was then later capable of harnessing her berserker power in a state that even Dragon Ball Super's Broly has yet to achieve- a Legendary Super Saiyan with mind intact.
6. Goku Black
Goku Black came about as the result of Zamasu traveling back in time and using the Super Dragon Balls to steal Goku's body. He's seemingly able to get a lot more out of it than the Saiyan too, as shown by his mastery of the Super Saiyan Rose form. He's strong enough to stand up to the full might of Goku, Vegeta, and Future Trunks and grows in strength further still with the help of the Potara earrings.
When fused together with the present-day Zamasu, he gains the power of immortality and this makes him nearly unstoppable and one of the very few series villains that Goku and his friends have been unable to overcome themselves. It instead requires the intervention of Zeno and the erasure of an entire universe to bring an end to his reign of terror.
5. Cumber
Cumber is a fairly recent addition to the world of Dragon Ball, but he's already made quite the impression with fans. In his Super Saiyan 3 form, he is able to hold his own against the almighty Jiren and defeated Top while barely breaking a sweat. He's an incredibly powerful fighter but is far from the best at this time.
As with most fighters, Cumber is no match at all for Goku's Ultra Instinct form. With the character's strength continuing to rise at a rapid pace though, there's every chance that the evil Saiyan could eventually surpass earth's protector in one of the upcoming arcs. He still has several transformations still to master and so should, at the very least, get a lot closer to Goku's level.