Billy

Adventure Time · Series · Former Hero of Ooo

Prime

Superhuman Physical Characteristics
Sword and Gauntlet Mastery
Great Hand-to-Hand Combatant
Large Size (Type 1; Towers over Finn and Jake and comparable to the Lich in size)
Energy Manipulation (The Gauntlet of the Hero shoots out a beam of energy)
Elemental Intangibility Negation (Can harm beings completely comprised out of water and fire)
Regeneration (Low-Mid; Regenerated his heart)
Weapon Control (Can summon his sword, Nothung, by saying its name)
Resistance to Mind Manipulation
Mind Control
and Perception Manipulation (Was unaffected by the Lich's passive Mind Control spells)
Fear Manipulation (Not afraid of the Lich)
Heat Manipulation (Punched a Fire Count and could stay in the Flame Kingdom without Flame Shield)
Cold Manipulation (When the Lich was in his body, he could slide down the lands of the Ice Kingdom, which could freeze Finn on contact)

None notable | Older Billy is weaker than his prime self, as well as rusty.

Ranked tied for #9 of 43 in Adventure Time by strength.

Billy vs Ladybug (Miraculous · Tier HIGH 5-A): Billy · Slight edge
Billy vs Champion (Terraria · Tier HIGH 5-A): Billy · Favored
Billy vs Monster X (IDW) (Godzilla · Tier 5-A): Monster X · Slight edge
Billy vs Zauriel (DC · Tier 5-A): Zauriel · Slight edge
Billy vs Zero (Kirby) (Kirby · Tier 5-A): Zero · Slight edge
Billy vs Cui (Dragon Ball · Tier 5-A): Too close to call
Billy vs Erza Scarlet (X793) (Fairy Tail · Tier 5-A): Too close to call
Billy vs Arc-Gurren Lagann (Tengen Toppa Gurren Lagann · Tier 5-A): Billy · Slight edge