Groundsplitter

Groundsplitter is a Whispering Death who was trained by Alvin the Treacherous

Appearance and Personality
Groundsplitter looks very similar to all the other Whispering Deaths that have been seen thus far in the franchise. Groundsplitter has the typical personality of its kind; highly aggressive, violent, and dangerous. With these character traits, it seems to be a perfect match for Alvin. With dragons like this at his command, Alvin has become far more dangerous.

Dragons: Riders Of Berk
In the episode We Are Family Part II, Alvin finally got his own dragon, the Whispering Death, Groundsplitter. Alvin had captured this dragon and caged it along with the other dragons on Outcast Island. With the help of Mildew, Alvin managed to trick Hiccup into revealing his dragon training secrets. Alvin tamed it along with Mildew in the Outcast Training Arena.

Dragons: Defenders of Berk
In Cast Out Part II, it is revealed that the Outcasts had more Whispering Deaths, one was being fed by Mildew, possibly Groundsplitter.

Another was the Screaming Death's mother. While she and her offspring left Outcast Island, it is possible Groundsplitter stayed behind.

Games
Groundsplitter's name was first mentioned in School of Dragons as one of the Flight Club courses. It was not mentioned who trained it.

Groundsplitter also became available in Rise of Berk.

Trivia

 * Groundsplitter is the first dragon trained by Alvin & The Outcasts.
 * Like all dragons trained by the Outcasts, Groundsplitter was captured and caged to be trained.
 * According to Rise of Berk Hiccup was close to training this dragon. When that happenned is unknown, considering that the only Whispering Death Hiccup tried to train on the TV show was Toothless' Rival.
 * This Whispering Death could be the Screaming Death's father.
 * Alvin didn't release all the Whispering Deaths as the mother Whispering Death and three babies were with the Screaming Death, so that could either be that Alvin kept the father Whispering Death and named him Groundsplitter.
 * Also, he kept some eggs from the mother Whispering Death.