Who killed the king on Game of Thrones?

There have been many kings and king pretenders, both in the show's history and current events.

King's Landing

Aerys II 'The Mad' - Killed by Jaime Lannister,

Robert Baratheon - Killed by a boar while hunting,

Joffrey Baratheon - Poisoned by Littlefinger and Olenna Tyrell,

Tommen Baratheon - Committed suicide.

War of the Five Kings

Robb Stark 'King in the North' - killed by crossbow bolt, shot by Roose Bolton,

Balon Greyjoy - thrown off a bridge to his death by his younger brother Euron,

Renly Baratheon - killed by a shadow assassin, created by Melisandre.

Stannis Baratheon - killed by Brienne of Tarth.