Okay so I know that Viltrumites have already been covered, but I just wanted to dive even deeper into how crazy of a combination it is.
So, for one, the Extinction Bomb (a planetary supervirus) being able to target specific populations/species and leave other beings alive, implies that genetic targeting is some facet of it. This would mean that Saiyans should be able to
successfully create a hybrid with a Viltrumite without said Hybrid having its DNA cannibalized and altered, as well as in itself show through being such a dominant trait that even if it were to fall victim, be so prominent it doesn’t matter.
While circumstantial, I think proof of this can be seen in Cell, whose DNA is a concoction of several different species and multiples of said species, (Vegeta, Goku, Frieza, King Cold, Gohan, Tien, Krillin, and Yamcha, potentially Roshi), and yet Saiyan DNA reigns most highly, or in their descendants from side/non canon material. Such as Goku Jr., who can turn SSJ despite being Goku’s
Great Great Great Great Great Grandson (that’s 5 Greats—There is a 6 Generation difference between them, and Goku Jr. is only 1/64th—Or 1.5625%—Saiyan). And if you include Dragon Ball Online, which goes an extra 100 years (and some change), the difference in Saiyan Blood is even
further. Though, admittedly, by then it’s gotten so low that you have to
Wish for SSJ, the benefits of it still exist. Intuitive Ki use, flight, super physicals, etc.
However, I’m going to assume it’s actually the former because it’s more accurate imo, and more interesting.
In this case, there’s already a lot to consider. For one, this Hybrid’s lifespan will be longer than any Viltrumite. While Viltrumites live for thousands of years, I don’t think we ever get a case for over 10K, but we do know that 2-3K is considered a tad younger, so with that in mind we can put the upper limit at 10. Saiyans have a strange set of aging. They stay incredibly young for a long period of time, then at adulthood get their adult body suddenly, and once that happens
maintain their youth (not aging, specifically,
to keep their prime), until they’re 80. We also know their lifespans
are longer than humans, but not by an
unreasonable amount. (“Not too differently,” in Toriyama’s words, so I imagine a few decades extra. This seems to be the case, because Paragus was a fullly grown and middle aged man, then lived with Broly for 40+ years, and despite his hair color, was still quite
physically capable with a PL of 4,200 {stronger than Nappa}).
For the purpose of this hypothetical, took the oldest person to ever live IRL (Jeanne Calmont of France at 122, rounded down to 120), and called that the average lifespan limit of the Saiyans (which seems fair, as our own life expectancy in comparison to her is usually at 80, especially when combined with the fact they're supposed to live decently longer than Humans, so 120 is really a lowball.) I then took that ratio of “Prime Age” (2/3’s of their life), and applied it to a Viltrumite’s “Age Limit” to get a good 16.6K years. Nearly double.
Next, assuming this immunity to disease from both the Saiyan and Viltrumite sides are combined, (most notably here, the Saiyan side), the Scourge Virus simply would not be effective on them. And the Extinction Bomb would be nothing but an annoyance. On top of this, their regenerative capabilities would be incredible. Viltrumites already have Mid-Low Regenerative capacity, and this is being compounded by the Saiyan’s
admittedly very limited Regenerative powers. (This allowed Vegeta to regain maximum vitality
considerably faster than normally estimated, but it doesn’t seem capable of quickly repairing injuries—Outside of Broly, who was able to completely heal from his internal explosion after 7 years of hibernation.)
So they’ll be able to get back up much quicker than any Saiyan or Viltrumite, and thanks to their Hybrid Physiology, they can fight through life threatening conditions. But more importantly, their energy cost would be virtually null. Goku was able to fight at max power after several months of starvation, Trunks could fight against Black at full strength after nearly a year(?) of basically not eating anything (him and Mai considered a singular tiny tin of cat food “a lot”), and Goku was able to straight up meditate (not eating or sleeping) for 150 days straight. Viltrumites excrete minimal toxins, allowing them to fight far longer and harder than anyone else around. They’ve been considered to have “Limitless/Infinite” Stamina in comparison to normal individuals (this is obviously exaggeration, but worth noting, and we have crazy stamina feats anyway, such as Nolan fighting for a year straight in a 1 war against a whole civilization, or holding his breathe and gaining the necessary resources from that for 2 weeks).
That’s to say not only would they be able to get back up and fight again, but the initial fight in itself will take substantially long. And that’s not including that Saiyans can quickly regain stamina from their Zenkai Boosts or muster up hidden wells power from totally exhausted bodies, or the adrenaline that can give Viltrumites a second wind. Mind you, Viltrumites have their own micro Zenkai Boosts, which will compound on each other.
Speaking of, this means that virtually every weakness a Saiyan has is gone. While they can’t breathe in space still, they can survive so substantially long in it doesn’t matter. Stamina isn’t a Saiyan “weakness,” but it’s a limitation, and it’s functionally gone now. Maybe you could include the Tail, but that can easily be trained away, and their Viltrumite durability/invulnerability completely removes it from being a real problem. (This also applies to their Ki Field for Combat.) Similarly, while Saiyan’s do resist a majority of disease, it’s not infallible, and the Viltrumite DNA fixes that. However, on the flip side their Saiyan heritage totally fixes the Viltrumite weakness. With a Ki Barrier, the extreme heat of a Star is meaningless. The Scourge Virus doesn’t work because Saiyan DNA. And while a specific frequency can cause equilibrium problems in a Viltrumite, Saiyan’s enhanced hearing has no such problems—I mean, we’ve reached a point where characters can scream so hard and loud they can poke a hole in space and time.
On top of all that, while the average Viltrumite definitely is outgunned by an average Saiyan (the
top tier 3 Viltrumites needed to band together and hit at the right time to destroy a destabilized/weakened planet, ranking only Small Planet, compared to the Average Low Class Warrior being able to casually throttle moon level opponents), they’re definitely substantially raising their base physicality and improving these low class warriors into greater heights due to Ki amplifying your base physicals.
They also benefit from having two flight methods, giving them perpetual and perfect flight control relative to their progenitors. Said Viltrumite Flight method, if we go by the Handbook, massively amplifies speed once you reach SoL via subatomic space-time jumps that hyper accelerate your apparent velocity beyond where it actually should be, and due to Smart Atoms, the body naturally compensates and gives proportional reaction speed. And assuming Ki continues to completely ignore physics in this context, (allowing for equivalent speed to that without the jumps) they get all the benefits of both with none of the cons. Allen will be stuck at Mach 10 in atmosphere to protect Earth, but the Saiyamite/Viltrian can freely move MFTL+ on planet (far beyond any Viltrumite, and probably most Saiyans).
On top of that, the Saiyan Forms would be freely accessible, which amplifies everything about them. Assuming typical Saiyan physicality, then probably limited to Oozaru and MAYBE SSJ, but that in itself is a major factor in itself. Those are 10x and 50x increases respectively, to
everything about them. Ki in itself is a major boost, too, and gives them an unparalleled range option, a new detection method (if they harness it), constant protective capabilities, crazy versatility were they to experiment, and even if they didn’t—They still have giant fireballs, their on demand lunar satellite (Power Ball), beams and blasts, barriers, telekinesis, (also, forgot to mention easy telepathy from Viltrumites), enhanced senses, can copy fighting styles and energy based attacks on sight, cause explosions and shockwaves, etc.
So, to close this out, within Invincible they’d be THE Ultimate Warrior, and within Dragon Ball they’d probably reign supreme on raw genetics, a totally flawless fighter, until the Android Saga in power, (where they’d then need to train in the ways of an Earthling to get the benefits the canon Saiyans have that allowed them to venture as far as they had.)
