I would have to agree with Frank.
If you type in on a google search, for example, any famous person (it doesn't matter how they became famous, just that they have the notoriety to be visible in a search) then click on a link that features their name via an "astrotheme.com" link, you'll see, when you scroll down, a bar chart that shows which planets are more dominant than others in their natal chart. In my opinion, this tends to show which planets are the most significant. I had been trying to see if there was a free sample version, since I've had my chart done and interpreted professionally twice now and only needed to know which planets were dominant. However, given what a friend shared with me, I believe I already know. Still, it would be nice to confirm it.
A while ago, there was a briefly heated discussion on another thread about the Sun being the most significant, citing a link between astronomy and astrology, but as I saw it, the size and non-astrological impact had little, if no bearing on its astrological influence.
As for how--given one's natal chart and the aspects involved--dominance is calculated, at the moment that feels beyond my knowledge, although I'd be very anxious to learn.
Longer answer to a shorter question, lol.