Kunzite ( )
The Anime Story
He was the fourth to serve Queen Beryl but was definitely the strongest of them. His battle was for the Silver Crystal that Sailor Moon aka Princess Serenity had in her possession. He blamed the Sailor Soldiers for Zoisite's death and that became his motivation. His youma were possessed humans so to destroy them meant killing innocents. He was the only shitennou to be killed by the soldiers.
The Manga Story
He was the highest ranking shitennou, but did not share a relationship with Zoisite. He served Beryl very loyaly, but later discovered that he once served Endymion. Later he was destroyed.
Kunzite was a calm and patient villain. He kept his emotions very controlled, even with faced with defeat. He seemingly became jealous when Endymion joined the Dark Kingdom. And his sorrow for the loss of Zoisite drove him to fight against the Sailor Soldiers fiercely.
30 Below | In Memory of Kunzite: King of Kawaii | The Kunzite/Malachite Shrine