Genthru is a Greed Island player. At first he works together with a big group of players, monopolizing defense spell cards so they can steal people's cards using offense spell cards.
Genthru is the player killer know as "Bomber". He betrays his group by using his Nen ability. Genthru has two main attacks: Count Down and Little Flower. He activates Count Down by touching someone and saying the word "Bomber" in a sentence. An invisible bomb is activated, exploding on the command "Release". The bomb is deactivated when saying "I've caught Bomber" while touching Genthru. This is prevented by Little Flower, allowing Genthru to explode whatever he touches. Explaining his Count Down ability to his target is required for it to work.
When pretending not to be Bomber, Genthru explains to Gon and Killua that Bomber is "most likely a Manipulation or Emission type user".