The fist technique the Stone Giants used was a high-tier martial art Heaven's Secret Fist from Heaven's Secret Valley. Even though their realm was not high, only seventh or so, with the materials used to create the puppets, the Stone Giant itself could be considered as a medium-grade masterpiece. Its combat ability was then naturally raised to a relatively high level.
The Stone Giant itself also did not have any vital weaknesses. Their resistance to physical attacks was incredibly great. They were very sturdy and could resist many blows, and with the puppet trap arts that increased their movement speed, the overall combat abilities of Stone Giants could be said to have no weaknesses that a player could exploit. There were no strategies that could be deployed against them.
If anyone wanted to train using Stone Giants, they would have to form a huge party and take turns to fight them one by one!