Ultimate boss

Ultimate bosses are enemies that appear as completely optional bosses with powerful capabilities. What sets them apart from other optional bosses are the fact that they are the strongest enemies in the games they appear in, often requiring amazing levels of power and extensive strategies to defeat.

Ultimate bosses are typically hidden, have certain conditions, and are always in the end game, if not during a second cycle or new game plus. Some even require that several other optional bosses be defeated first in order to reach them.

Ultimate boss characters

Shin Megami Tensei I & II

• Beelzebub (Neutral and Law route in I & II)

Shin Megami Tensei: 20XX Devil's Colosseum

• God

Shin Megami Tensei III: Nocturne

• Lucifer (True Demon Ending's last boss)

Shin Megami Tensei: Strange Journey / Redux

• Demiurge (New Game + only, Alilat must be defeated and the final Enemy Search must be acquired prior)
• Belial, Nebiros, Lucifuge, and Beelzebub (Fought separately in a Redux New Game + only; must be on one of the new endings)

Shin Megami Tensei IV

• Masakado's Shadow (DLC)

Shin Megami Tensei IV Apocalypse

• Stephen (DLC)
• Fiend Race ("Depths of Twisted Tokyo" DLC and multiple cycles)

Majin Tensei II: Spiral Nemesis

• Angra Mainyu (Neutral Route)

Shin Megami Tensei: Devil Summoner

• Nanto Seikun and Hokuto Seikun (Must trigger the event flag by being right front of the door leading to Inaruna's burial chamber)
• Enoch, David, Leviathan and Squall (PSP version only; must have finished the game, and defeated Nanto Seikun and Hokuto Seikun; the four can be as an entire group during a New Game+)

Devil Summoner: Soul Hackers

• Devil Summoner protagonist (PlayStation and 3DS version only and only in the EX Dungeon after finishing the game)
• Raidou Kuzunoha the XIV and Raido Kuzunoha the XIV (3DS version only and only in the EX Dungeon after finishing the game and after defeating the protagonist of Devil Summoner)
• Soulless God Oumagatsu (3DS version only in the EX Dungeon. Must beat Raidou and Raido before facing him).

Devil Summoner: Raidou Kuzunoha vs. The Soulless Army

• Beelzebub (Reach the last floor of the training hall)

Devil Summoner 2: Raidou Kuzunoha vs. King Abaddon

• Masakado (New Game +, neutral alignment, and 99% completion of Case Files)
• Lucifer (New Game + and Chaos alignment last playthrough)

Persona 2: Eternal Punishment

• Philemon (EX Dungeon only)

Persona 3 / FES / Portable

• Elizabeth (2nd cycle*. Must accept her request and reach the top of Monad.)
• Theodore (P3P only, optionally replaces Elizabeth when playing as the female protagonist.)
• Margaret (P3P only, must have spared Ryoji Mochizuki on December 31 and completed all challenges in the Vision Quest.)

Persona 4 / Golden

• Margaret (2nd+ cycle only, Empress Social Link must be maxed, and all optional bosses must be defeated after rescuing someone)

Persona 4 Arena

• Elizabeth (last foe of Score Attack)

Persona Q: Shadow of the Labyrinth

• Elizabeth, Margaret and Theodore (2nd+ cycle, must complete the game on both the P3 hero's and P4 hero's routes)

Persona 5 / Royal

• Caroline and Justine (New Game+ only)
• Lavenza  (Royal only, New Game+ only)

Persona 5 Strikers

• Boss rematch quests post-game
• The Reaper

Persona Q2: New Cinema Labyrinth

• Velvengers (Caroline and Justine only > Caroline and Justine and Margaret > Caroline and Justine and Theodore > Caroline and Justine and Elizabeth) (After completing all quests)

Digital Devil Saga: Avatar Tuner

• Demi-fiend (2nd cycle only, reach the end of the Karma Temple and return to the Anahata basement before fighting the final boss)

Digital Devil Saga: Avatar Tuner 2

• Satan (Hard difficulty only)

Devil Survivor

• Lucifer (New Game + only, on any non-Yuzu route)

Devil Survivor 2

• Alice (with Nebiros and Belial, the two having been defeated prior)
• Tico Duo (Record Breaker only, must acquire the right to fight them while starting a new game, which will cause a special event to appear on Friday at 19:00 on the Triangulum arc only)

Mechanics
Franchise-wide
Demon - Magic (Fusion Spell) - Battle Stats - Damage - Accuracy - Experience - Level - Element - Extra Skills - Critical - Status effects - Macca - Yen - Magnetite - Incense - Alignment - Moon Phase System - Demon Summoning Program (COMP) - Cathedral of Shadows (Fusion - Skill Inheritance - Accidents / Special / Three-demon / Sacrificial / Sword) - Demonic Compendium - Evolution - Special conversation - Rag's Jewelry - Code Breaker - Turn Press - New Game Plus - Ultimate boss - Streetpass - Password - Difficulty - Skill Mutation - Energy Drain
Shin Megami Tensei series
Terminal - Guardian (if...) - RTS (NINE) - Plugins (NINE) - Magatama (3) - Reason (3) - EX Missions (SJ) - Challenge Quest (4) - Whisper event (4) - Smirk (4) - Barrier (4) - Partners (4A)
Devil Summoner series
Loyalty - Personality - Mystic Change - Nemechi (SH) - Case Files (RKKA)
Majin Tensei series
Rank - Affinity (2) - Arcana (Ronde)
Persona series
Shadows / Personas (Initial / Prime / Ultimate / Ancestor / Reverse / Sub) - Skill Card - Totem (1) - Type/Subtype (1+2) - Affinity (1+2) - Rank (1+2) - Mystic Change (1+2+5) - One More (3-5) - Growth Rate (1+2) - Unknown Power (1+EP) - Personality (1+2, 5) - Material Card (2) - Mutation (2) - All-Out Attack (Cut-in) - Heart Item (3) - Shuffle Time (3+4) - Daily Life (3-5) - Calendar (3-5) - Social Stats (3-5) - Social Link (3+4) - Tactics (3-5) - Requests (3-5;Q+Q2) - Arcana Chance (4) - Forecasts (Fusion / Weather) (4+5) - Guard (3P+4+5) - Boost (Q+Q2) - Power Spot (Q+Q2) - F.O.E (Q+Q2) - Confidant (5) - Technical (5) Treasure Demon (5) - Party Switch (5) - Disaster Shadow (5R) - Fusion alarm (5R) - Persona Traits (5R) - Third Eye (5) - Master Arts (5S) - BOND (5S)
Devil Children series
Trainer - Bank - BattleNet - Relic Fusion - Power Fusion - Powers
Digital Devil Saga series
Berserk Mode (2)
Devil Survivor series
Devil Auction - Extra Turn Battle - Skill Crack - Titles (DSO / DS2 / RB) - Fate System (2) - Add-On (2)
Other
Equip Type (GMT:TM) - Class Change (TMS♯FE) - Topic System (TMS♯FE) - Side Quests (TMS♯FE) - Ad-lib Performance (TMS♯FE) - Session (TMS♯FE) - Dual Arts (TMS♯FE)