The Chimera Ants Arc: Hunter x Hunter(1998)
overview
Welcome to one of the best arcs in Anime history. The Chimera Ants arc is incredible. When ants begin to mutate and take on the physical abilities of whatever species they eat, the earth faces the threat of being ruled by ants. They gain intelligence and human abilities when the ant queen begins to consume live humans as well. When the ant king is finally born, he is a cold hearted vicious beast, along with his subordinates. Gon, Killua and their compatriots invade an area the ants have taken ownership of in an effort to save everyone and everything. Its incredibly awesome!
sPOILER aLERT!
One of the King' subordinates, Neferpitou, kills Kite in an epic battle. She then beheads him and uses soul less body as a weapon. This enrages Gon leading him to risk it all just to make sure Neferpitou dies.
The Chimera Ants Arc: Hunter x Hunter