How zenkais work (theory)

[Hector]

Zenkai is not a random increase. It makes you as strong as the greatest power you have experienced so far.

-Vegeta (post Earth) became equal to Kaioken 3x Goku.
-Vegeta (post Zarbon) became equal to Monster Zarbon.
-Vegeta (post Recoome) became as strong as Freeza's 1st Form, because, due to his lack of sleep, the zenkai couldn't be completed immediately. Later, he sensed Freeza approaching right before waking up (waking up completed the zenkai, thus making him as strong as the largest chi he had felt until then).
-Vegeta (post Krillin) was healed by Dende moments after Freeza transformed, so he sensed 4th Form Freeza's initial power and the zenkai brought him to that level.
-Goku (in the healing tank) sensed Freeza's chi when he sped up against Vegeta and when he exerted his max effort (pre 50%) to deflect Vegeta's blast (that max effort was equal to the No Hands power he used against Goku later), so his full base power became equal to No Hands Freeza.
-We can assume Gohan became as strong as Recoome after his zenkai, leaving aside his anger boost. Nothing contradicts that.
-Gohan (post Freeza zenkai) was brought close to the level of the Freeza that had just beaten him.

 

[GSM123]

TL;DR they become strong enough for their plot necessities to be fulfilled

But yeah I always thought it worked like this, albeit very loosely. This plus the idea that Zenkais keep getting larger the closer a Saiyan gets to Super Saiyan. Vegeta’s Zenkai post Recoome only works if you go by the nap theory, and Goku seems a bit of a stretch as well.

There’s also Goku’s Zenkais in his spaceship though the mere fact Goku was giving himsef zenkais despite Vegeta saying it’s impossible is a inconsistence of itself.

 

[Captain Cadaver]

It was pretty clear that Galu after getting the senzu in the hospital wasn't as strong as 18k Vegeta or Oozaru Vegeta, so no.

I'd say GSM's take that Saiyans get greater Zenkais the closer they get to Super Saiyan is far more coherent, given it also lines up with the idea of the increase in S-Cells. There is some evidence for the OP's hypothesis in Vegeta's explanation that the stronger an opponent, the stronger a Saiyan can get, but that doesn't necessarily mean they'll be automatically elevated to the level of whowever they fought or sensed.

There’s also Goku’s Zenkais in his spaceship though the mere fact Goku was giving himsef zenkais despite Vegeta saying it’s impossible is a inconsistence of itself.

I'd say intent is what made Goku's training an exception, since he wasn't fully aware of how Zenkais worked which may have allowed him to exploit it initially whereas Vegeta couldn't through knowing full well what he was doing. Zenkais are a biological trait, after all, so the neurological impact of the brain and its mindset may have affected them as well.

 

[SSJ2]

All of this is invalidated by Vegeta having sensed Freeza's ki from a young age. Why didn't his first Zenkai bring him to 1st Form Freeza's suppressed level at the least?

 

[GSM123]

Vegeta was so loyal to Freeza he didn't count him on the zenkai. Only when he was fighting the Ginyu Tokusentai he was 100% sure he hated Freeza and got as strong as him.

 

[Papasmurf]

All of this is invalidated by Vegeta having sensed Freeza's ki from a young age. Why didn't his first Zenkai bring him to 1st Form Freeza's suppressed level at the least?

Vegeta couldn't sense ki until after his fight with the Z senshi on Earth.

 

[Hector]

All of this is invalidated by Vegeta having sensed Freeza's ki from a young age. Why didn't his first Zenkai bring him to 1st Form Freeza's suppressed level at the least?

Maybe because he hadn't sensed him in years.

 

[Hector]

It was pretty clear that Galu after getting the senzu in the hospital wasn't as strong as 18k Vegeta or Oozaru Vegeta, so no.

Actually, nothing proves he didn't become as strong as Earth Vegeta after that zenkai.

 

[Captain Cadaver]

Actually, nothing proves he didn't become as strong as Earth Vegeta after that zenkai.

He was excited about the prospect of fighting someone stronger than Vegeta as well as worried about it, knowing he'd need to push himself far beyond his current level. Hardly a reaction someone would have if already as strong as him and capable of doubling their power without serious risk. For what it's worth, you also have the DBZ Movie 3 pamphlet displaying a post Saiyan Arc Base Goku at 10k. Moreover, you have nothing proving he did beyond your very flawed theory.

Maybe because he hadn't sensed him in years.

He'd never sensed him at all prior to Namek, and if sensing was enough to elevate him to Freeza's level as you suggested with your Goku example, there's no reason Vegeta wouldn't have hit that level after his Zenkai from Zarbon.

 

[SSJ2]

All of this is invalidated by Vegeta having sensed Freeza's ki from a young age. Why didn't his first Zenkai bring him to 1st Form Freeza's suppressed level at the least?

Vegeta couldn't sense ki until after his fight with the Z senshi on Earth.

True, but going by this theory he couldn't sense Goku either on earth. So he would only know of their battle powers from Scouter readings.

 

[Papasmurf]

I don't see how knowing someone's numeric battle power value would help at all in making the body strengthen itself from a Zenkai.

 

[SSJ2]

I agree. This theory has no basis.

 

[Hector]

Zenkai is a physical/mental process. Either being hit by a certain power or sensing it with your biological senses makes your chi (which is a combination of body and mind) 'memorize' that power and evolve you to reach that level. Of course, sensing it isn't enough. You have to be able to properly gauge it as well, which is why one cannot just reach Beeruses level with one zenkai. Vegeta couldn't properly gauge Freeza's power when he was still infinitely weaker than him.

 

[GSM123]

It was pretty clear that Galu after getting the senzu in the hospital wasn't as strong as 18k Vegeta or Oozaru Vegeta, so no.

Actually, nothing proves he didn't become as strong as Earth Vegeta after that zenkai.

On top of what CC said he can’t possibly be as strong as Oozaru Vegeta, the true highest power he’s experienced. Plus what about Gohan? Did he not get a zenkai after the fight as well?

All of this is invalidated by Vegeta having sensed Freeza's ki from a young age. Why didn't his first Zenkai bring him to 1st Form Freeza's suppressed level at the least?

Vegeta couldn't sense ki until after his fight with the Z senshi on Earth.

True, but going by this theory he couldn't sense Goku either on earth. So he would only know of their battle powers from Scouter readings.

Pretty sure taking Goku’s attacks head on is way closer than just sensing. Keep in mind OP talks about power experienced, not sensed.

 

[SSJ2]

[mention]GreatSaiyaman123[/mention]

completed immediately. Later, he sensed Freeza approaching right before waking up (waking up completed the zenkai, thus making him as strong as the largest chi he had felt until then).
-Vegeta (post Krillin) was healed by Dende moments after Freeza transformed, so he sensed 4th Form Freeza's initial power and the zenkai brought him to that level.
-Goku (in the healing tank) sensed Freeza's chi when he sped up against Vegeta and when he exerted his max effort (pre 50%) to deflect Vegeta's blast (that max effort was equal to the No Hands power he used against Goku later), so his full base power became equal to No Hands Freeza.

None of these examples had anything to do with physically experiencing a power.

The theory itself is bogus. Why in some instances does it revolve around physically experiencing a power and others it depends on a power being sensed. All of these examples are contracted by Gohan and Vegeta having sensed suppressed first form Freeza initially on Namek. Suppressed Freeza was never noted to power up, and we know from Nail that not even post Kaio Piccolo would have been a match for him. So why didn't their first zenkai result in such a major increase? The answer? The theory is bogus.