Before Monkey D. Dragon shows up there are 3 phenomenons:
Ok Dragon is a Zoan type but not just any Zoan type, he won’t turn into a Wind Dragon or a Thunderbird, he is different.
Sengoku “The Buddha”
We’ve seen Sengoku turns into a Buddha, he has the power to create a huge shockwave enough to stop Blackbeard and his crew but… The Buddha has lots of other powers:
•Iddhi: power over matter like walking on water and through earth and walls.
Though we’ve never seen him using these abilities he would have these.
But Sengoku has to change forms in order to use these abilities while Monkey D. Dragon doesn’t change forms when he uses his phenomenons, so this is the devil fruit he has: Roman God: Jupiter.
The Roman God is an equivalent to the Greek God Zeus but Zeus has a lightning bolt while the Roman God Jupiter is known as a Weather God having the abilities to control:
Now Dragon has caused all these phenomenons but he remains in his Human Form
How does Dragon use his Mythical Zoan powers without changing his Form?
In Whole Cake Island arc Jinbe stated that Charlotte Katakuri has a Special Paramecia type of devil fruit that gives the user the abilities of a Logia type of devil fruit but that’s Super-Rare.
Dragon’s current devil fruit is Ultra-Rare type of devil fruit that gives the user the abilities of a Mythical Zoan devil fruit while remaining in his human form so it’s a special Zoan Type of Devil Fruit that gives the user the ablities of a Paramecia Type, thus explaining how he could use his powers with his Human form.
How powerful is this Devil Fruit and why Dragon is the Most Wanted Man Alive?
The Roman God Jupiter is the God of Gods and Mythical Zoans mostly portray God like creatures such as Marco’s Phoenix but the term God of Gods means that Dragon is now equal to Zeus and Zeus is the most powerful God.
So the reason why the World Government wants Dragon’s head is because he possess the most powerful devil fruit in the whole series and that power is alone enough to destroy the World Government.
Thank you for reading.
*Theory by King of beasts kaido