Is there any evidence that points to which is stronger, either reaching max level of Kaio-Ken or the max level of Super Saiyan? When Goku reached the highest level of Kaio-Ken, he seemed like he could take out the strongest Super Saiyans.
Kaio-ken is clearly inferior to his Super Saiyan state. Once Goku is able to sustain his Super Saiyan abilities, he stops even using Kaio-ken after a time. He was unable to assume the powers of the Super Saiyan when he returned to life to battle Freiza, so he used the power extending abilities of the Kaio-Ken which increased his power by multiples. Goku was the only known practitioner of the Kaio-Ken technique.
The Kaio-ken was not a natural extension of the Saiyan powers, it was taught to Goku by King Kai, who invented the power but was not capable of using it. The greatest weakness of the Kaio-Ken was the terrible strain it placed on Goku's body. After its use Goku was completely depleted of energy and unable to utilize any physical abilities for quite some time.
When Goku first mastered the Kaio-ken, the furthest he could handle was the Kaio-ken x4, but through training at 100x gravity and then later with his dramatic strength increase after his fight with Captain Ginyu, he was able to withstand astounding multiplications of the Kaio-ken technique, such as Kaio-ken x10. The highest multiplication for the Kaio-ken ever seen was the Kaio-ken x20, which Goku used against Frieza. --Dragonball Wiki
The Super Saiyan state is a more natural extension of the Saiyan species and once mastered can be maintained much more effectively and without the side-effects of the Kaio-Ken. It however requires a Saiyan to achieve a significantly higher state of battle mastery and thus was unseen for quite some time among the Saiyans.
Given a confrontation between a Saiyan with Kaio-ken and a Saiyan without it, the Kaio-ken, especially if the practitioner is experienced, is superior. However, a confrontation between the Kaio-Ken and the Super Saiyan would almost always leave the Kaio-Ken user, defeated. Super Saiyan level 1 is far superior to the Kaio-Ken even at the times 20 level.
In Dragon Ball Z: The Return of Cooler, Goku again uses the Kaio-ken on Meta Cooler, but it again proves far too feeble, forcing Goku to go Super Saiyan soon after. --Dragonball Wiki
It has been shown (one time) that the Kaio-ken could be stacked on top of the Super Saiyan powers but the strain on Goku was so great it was believed it could even kill him. He used this power arrangement in a battle against Pikkon.
3Important note: Super Saiyan + Kaio-ken probably would have killed Goku if he wasn't already dead at the time.– DampeS8NJun 19, 2012 at 20:15
Super-kaio-ken would have done no harm to goku, it could have just exosted him a bit, because goku had a great power than pikon, but the only think he needed to master was the speed, he was unable to keep up with the speed of pikon, that is why it appeared as if he was loosing the fight but he then uses the instant transmission technique to win– user12354Feb 3, 2013 at 18:23
3This needs to be edited. Goku didn't return to life to battle Frieza, he returned to life to battle the Saiyans. Goku never died in his fight with Frieza and never lost the Super Saiyan ability during that fight. He also was not able to transform into a Super Saiyan during his initial battle with Frieza, hence the use of Kaio-Ken.– RobertDec 23, 2014 at 16:52
Actually, in the manga he went to i think 30 in the frieza fight when tien was being a smart alek and said Goku has already won because he could go x20 but King Kai replied saying he was already using the Kaio Ken x30 (Might've been 40)– user44738Apr 24, 2015 at 1:38
Any evidence of compounding the two power ups? SSJ4 + Kaioken x40 or something crazy. ;)– StormieFeb 15, 2016 at 8:29
Super Saiyan is stronger. Goku could take Friza in his final form as a Super Saiyan but couldn't scratch him in Kiaoken x 20. Not only that, but the number of times Goku would have to increase the Kiaoken output it would put too much strain on his body, so once it wore off he would either not be able to fight anymore or he would die.
Technically, there is no "Max level of Kaio-Ken". You could go up to Kaio-Ken 2,000,000 if your body could withstand it.
The highest level of Super Saiyan is Super Saiyan 4 or Super Saiyan God super saiyen, going by canon.
Because your power is increased, your ability to withstand more of the Kaio-Ken should be increased as well. So I would say the "Max level of Kaio-Ken" is stronger by far.
As mentioned in Thaddeus's answer, Goku did use Kaio-ken on top of Super Saiyan once.– IzkataJun 30, 2013 at 5:09
Sounds like kaioken could be used to acclamante the body to strain to train for SS. A higher level SS should also be able to use a higher level of kaioken. Furthermore, sounds like kaioken shoulda been something that krillin, tien, and yamcha jumped on during their time with king kai. Since there's no SS transformation for humans, that would be an awesome tool for those characters. Plus, by later in the show (say, cell saga) I think we can safely assume that those characters are at least about as strong as goku was after he fought Ginyu but before he went SS, meaning they should each be resilient enough for masterful execution of kaioken - x10 or even more.
Super Saiyan is superior because kaioken has the side affect of strain and as king Kai said "total obliteration" while in super saiyan it multiplies the saiyans strength several times and the strain is minimal to non existent.
In conclusion super saiyan is superior due to the fact that even if super Saiyan has a limit and kaioken doesn't ,kaioken is only to be used in short bursts as king Kai has said that it's only limit is your own and no one not even goku at his peak can reach kaioken 2,000,000 and if anyone did they would die or it would wear off leaving the fighter drained and useless. Super saiyan is superior in every class except limits but the limits are the users limit deeming it inferior and I am sorry if this angers anyone but it is true.
King Kai said this when Goku completed his training on other world.
He was explaining how the Kaioken worked and that it was only to be used in short bursts
I did some research and realized that in the episode counting down king Kai explains that kaioken could lead to your own destruction meaning since super saiyan has a lack of that risk and multiplies all attributes x 50 for an unprecidented amount of time it means super Saiyan is superior and Kaiden can only be sustained for a short period of time. Supersaiyan is superior.
Super Saiyan is stronger than Kaio-Ken
Super Saiyan is a natural extension of the Saiyan race, which is accomplished by gradual training and experience.
Before the Cell's Tournament, when Goku and Gohan are training in the Hyperbolic Time Chamber, Goku recommends that Gohan should keep his Saiyan state, even when they weren't training, so the body would get used to it.
Kaio-Ken is essentially a power multiplier, boosting strength, speed, reflexes and all other fighting abilities.
This technique is used to temporarily overload the user's body with enhanced capacities for a limited time, depending on each body's resistance.
Not to mention that Kaio-Kun is very rough to the body:
The technique, however, has its substantial flaws. If the user multiplies their base ki too much, the uprise of ki could easily obliterate them, or severely damage their body, as it did Goku's.
After using the Kaio-ken x4 to overpower Vegeta's Galick Gun, Goku's entire body was thrashed, and he could barely move without hurting himself.
Source: Dragon Ball Wikia
At the moment, there is a new reference to Kaio-Ken being used by Goku as SSGSS. Theoretically, it's not recommend that a Super Saiyan uses Kaio-Ken since this process would much likely kill the user.
As a SSGSS, it is now possible to surpass this restriction:
Goku obtained the Super Saiyan God Super Saiyan form - which possessed great ki control, utilizing the Kaio-ken technique alongside it became possible.
Source: Dragon Ball Wikia
Conclusion: Since Kaio-Ken is limited by the user's body fortitude, developing the Super Saiyan form allows someone's body to reach higher Kaio-Ken level multipliers.
This means that Super Saiyan form determines whether or not Kaio-Ken is safe to use.
Kaio-ken is technically the more powerful technique in terms of max raw power output possible. Someone could, in theory, push their body to become use to ever higher levels of it. The draw back is extreme damage and exhaustion to the body. It's like over clocking a CPU, the higher you go the more power you're going to get out of it, but you're damaging it, and it will quickly overheat and crash.
Super Saiyajin on the other hand is more like adding another core to the the CPU that you can activate and deactivate. You can add more power and access it longer, but the CPU takes more damage from normal wear and tear over the course of it's life. The more you use it, the more you lessen the life span of the CPU even though you won't crash. Also, so long as you don't over clock or over heat, you're going to be stuck at given power output for each core you add.
So which is "stronger" or better? Depends on context. Do you have a short time to live? Or, conversely, a long time to live? Do you need a greater boost right this second? Do you already have transformations? Can your body hand the stressing? Can your body handle transformations? Based on these questions the answer changes... If you're at Super Saiya-jin 3 and you're seeing the constraints of the transformations you can get to already I'd think it's is probably wiser to invest my time into getting to higher levels of Kaio-ken. On the other hand if there is a known legendary transformation that is ultra powerful, I'd go with looking for that transformation. Likewise. if I have a long time to live and train I'm going for training Kaio-ken, not mastering Super Saiya-jin.
The answer is situational, but consider that Super Saiya-jin 3 is something like x200 or x400 and it takes 1 year to get to x20. Think about the results and possible results SSJ3 is, what, 10 years down the line and very problematic, leaving you in a state worse of than your max Kaio-ken does. If you progress at x20/year and we compare it to SSJ3, I'd much rather bet on Kaio-ken than SSJ3 and another 10 years down the line you'll have x400, and 10 years after that you'll have x600, where as if you just go with SSJ3, you'll still be stuck at x200 or x400.
So I'm gonna side with Kaio-ken overall. 3 years after getting Kaioken you can do x60, 3 years after getting SSJ you can do x50, 4 years it is x80 vs x50. so this becomes increasingly obvious which is "better" overall, but if you can get SSJ/SSJ2 there is no reason not to have it and use it instead of Kaio-ken x50 and x100? because SSJ/SSJ2 are decisively better provided you don't mind shortening your life or would prefer not to be physically exhausted/injured afterwards.
I would say that Kaioken and Super Saiyan are equal because there technically is no max level of Kaioken as mentioned ealier, and there is no specified amount in power increase from Kaioken as Goku only said Kaioken increases the physical abilities of the user and never gave how much Kaioken increases the user's power by and it is said that Super Saiyan increases the Saiyans power by 50x the normal power.
In conclusion, Kaioken has no specific amount of power increase and technically no max level but puts an insane amount of strain on the body depending on the level of Kaioken being used, therefore it can not be maintained for that long however once Super Saiyan is mastered it can be maintained longer and used more effectively than Kaioken because it doesn't put that much of a strain on the body as Kaioken however Super Saiyan does have a max level so that is why in my opinion they are both equal.
This doesn't introduce any new information, and only acts as a specualtive counter to the accepted answer.– ZibbobzMar 3, 2015 at 19:48