The asteroid that wiped out the dinosaurs was just 6 miles wide.
This one is purported to be 20 times as wide, so, more or less 20 times in each dimension, or perhaps as much as 8000 times the mass of the Chicxulub impactor, while Ganymede is less dense than Earth and 3,275 miles diameter compared with 7,926 miles diameter of the Earth.
OTOH, the orbital velocity of Jupiter is only 43 percent that of Earth, and that would be in the ballpark of the velocity of this impactor on Ganymede. A lot of energy. The resulting density of Ganymede would be in part determined by the density of the impactor, so the ice that makes up a lot of Ganymede today will have come from the impactor.
https://www.britannica.com/place/Ganymede-satellite-of-Jupiter