After nearly 2 years trying, I finally got Prince Arthas after beating the Lich King with the help of Sn1p-Sn4p. Deck lists used are in the comments. : r/hearthstone
Beating The Lich King With Paladin - Hearthstone Decks
Kill Lich King w/Shaman - Galakrond's Awakening Hearthstone Decks - Out of Cards
A list for those whole haven't beaten Lich King : r/hearthstone
Decklist to defeating The LIch king - Year of the dragon version - イカ山の炉端放浪記 ハースストーンブログ