8. Kangaxx in Baldur’s Gate 2
This totally optional boss fight was easily the hardest battle in the game due to Kangaxx’s abilities as a demi-lich. Kangaxx could instantly kill members of your party—destroying them permanently and forcing a you to reload the game as there were no means to resurrect them from the dead if killed by his attacks. You had to be completely prepared to face a demi-lich with a wide assortment of scrolls and spells to face him down. The ring you get for killing him is one of the best in the game.