Arthas was, in his youth, a powerful paladin and prince of Lordaeron. he fought alongside the likes of Jaina Proudmore and battled the forces of the Scourge. However, he was eventually drawn to Icecrown to claim his place as the Lich King, taking the mantle of Frostmourne, and with it, the former Lich King's soul. Arthas returned and slaughtered his people and built one of the mightiest armies of Azeroth.
Arthas would eventually be slain by the combined forces of the Horde and the Alliance after many ages of fighting. His Death Knights had turned against him, his armies were scattered, and he was slain, only to have Tirion Fordring take his place as the Lich King.
Powers and Stats
Tier: Probably 5-C
Name: Arthas Menethil, The Lich King, King of the Scourge, Frozen King
Classification: Death Knight, Lich King, Former Paladin, Undead Lord
Powers and Abilities: Superhuman Physical Characteristics, Death Manipulation, Necromancy, Magic, Telekinesis, Telepathy, Fear Manipulation, Mind Manipulation, Mind Control, Summoning, Destruction, Ice Manipulation, Blood Manipulation, Biological Manipulation, Illusion Creation, Portal Creation, Rage Power, Instant Kill Powers, Teleportation, Aura, Soul Manipulation and Durability Negation via Frostmourne, Master Melee Fighter, Martial Arts, Resurrection, Shadow Manipulation, Fire Manipulation, Absorption, Immortality (Types 1, 6, and 7), Pain Manipulation, Earth Manipulation, Life Manipulation, Statistics Amplification, Athleticism, Life Support
Lifting Strength: Unknown, possibly Class M via Telekinesis (Capable of lifting enormous temples into the air passively)
Striking Strength: Unknown
Durability: At least Small Moon level, probably Moon level (The Dragon Aspects were literally powerless to stop him without some help), Plate of the Damned makes him immune to most forms of actual harm, including physical and magical
Stamina: Very high, possibly endless
Range: Dozens of meters, planetary with telekinetics/telepathy and mind manipulation (it gets weaker the further you are, however)
Standard Equipment: Frostmourne (Soul-Stealing Sentient Sword), Plate of the Damned, Mantle of the Lich King, Helm of Domination
Intelligence: At least Genius, outdid the various military leaders of the world for ages before finally being defeated
Weaknesses: To a small degree, holy magic; it must rival his own for this to matter, however