As the many above me have said, Earth magic. Usually whenever I come across a protagonist who is proficient in elemental magic, he's usually a fire or water, with the former occuring the most. Probably because fire is known for its destructive power.
If its not one, its usually all of them. "Jack of all trades", I think it was called.
But Earth is strong too, you know. That's why I can appreciate protagonists who primarily use Earth magic, like Rudeus Greyrat from Mushoku Tensei, with one of the spells that he use a lot, is just Rock Bullets. But he's learned to cast them so quickly and potently that its now a machinegun, or rather a shotgun, if he wants it to be.
One more thing, he literally makes multiple mech suits to amplify the rock bullets even FURTHER.
Add the fact that said mech suits were actually created using primarily Earth magic as well for the raw materials.
There was some kind of other enchantment related magic circle stuff in there as well for the circuitry, but the stuff it was made out of was done using Rudeus' own earth magic.
Honestly, I don't think that gravity is a part of the earth magic. Demolishing things is easier, true. But, it's not that op if we are talking about one-on-one action or small scale, group fights.
Sometimes it's considered separate, sometimes it's considered an evolved or higher form. It really depends on the writer.
I think one of the more under-sold things though would be the freedom of mobility the earth element would offer. A skilled earth magic user would also be able to create an opening in a solid stone surface, and also enclose themselves inside for something of a "turtle" strategy. But, it's not just bunkering down and hiding. With some more effort, said earth mage could actually start travelling underground and re-position themselves.
It's also good for creating fortifications, not just destroying infrastructure.
That's the thing. A lot of people tend to think of earth magic as brutish. However, a lot of the element's most powerful applications are actually incredibly strategy based. It might just be the most intellectually involved of all the elemental powers.
I'm not sure about 1 on 1 fights, but if it comes to nation building then my money is always going to be on the country heavy in earth mages to take over the world.
Water mages might be able to grow crops in the middle of a desert, but so long as an earth mage can find a river they can use their earth magic to divert it and create a canal system. So, no need for water mages at the lower levels of technological advancement.
Fire mages might be able to advance more quickly once you get into the steam age, but you need a lot of civilization advancements before you get to that level and earth mages are going to advance through every one of those earlier ages FAR faster than people using any other element. By the time you even get to the steam age, a nation of earth mages could just enlist a small group of fire mages to work on their machinery. (Possibly as slave labor.)
About the only area any other element has an edge is seafaring exploration. Both wind and water mages would have an edge in that area. That can be used to form trade routes. However, with the riches that an earth-elemental using nation would have, they can easily become a powerful importer nation and profit off the wind and water mage merchant class.
In short, earth mages are the ones who would really take over the world.