I haven't seen any stats for the mightiest commander of Demogorgons horde of demons so I decided to stat him. Enjoy!
Supreme Commander Belcheresk CR 27
Male Advanced Balor Fighter 4
CE Large Outsider (Tanar’ri)
Init +9; Senses Dark Vision 60ft, True Seeing
Speed: 30ft (40ft w/o armor), fly 90ft (good)
AC: 45, touch 16, flat-footed 39
HP: 641 (30 HD) Fast-Healing: 6, DR: 15/cold iron and good, DR 5/-
Immune: electricity, fire, and poison
Resist: acid 10, cold 10; SR 38
Fort +32, Ref +23, Will +23
Melee:* +1 Dancing Vorpal Great Sword +31/+26/+21/+16 (3d6/19-20/x2) and
+1 Flaming Speed Long Sword +37/+37/+32/+27/+22 (2d6+24 plus 1d6 fire/ 17-20/x2) and
+1 Wounding Frost Whip +36/+31 (1d4+15 plus 1d6 cold plus 1 Con plus entangle)
*8-point Power Attack
Space 10ft.; Reach 10ft (20ft with whip)
Base Atk +30; Grp +49
Atk Options: Cleave, Devastating Critical, Great Cleave, Overwhelming Critical, Power Attack
Special Actions: Death Throes, entangle, mighty rage 1/day, spell-like abilities, summon Tanar’ri
Spell-Like Abilities (CL 26th)
At Will-blasphemy (DC 27), dominate monster (DC 29), greater dispel magic, greater teleport, insanity (DC 27), power word Stun, telekinesis (DC 25), unholy aura (DC 28)
3/day-quickened greater dispel magic
1/day-fire storm (DC 28), implosion (DC 29)
Abilities: Str 40, Dex 25, Con 40, Int 24, Wis 24, Cha 30
Feats: Cleave, Devastating Critical, Fast Healing (2), Improved Toughness, Improved Two Weapon Fighting, Improved Critical (long sword), Over Whelming Critical, Power Attack, Quicken Spell-Like Ability (greater dispel magic), Two-weapon Fighting, Weapon Focus Long Sword
Skills: Bluff +43, Concentration +48, Diplomacy +48, Disguise +20 (+22 acting), Hide +36, Intimidate +45, Knowledge (history) +30, Knowledge (planes) +40, Listen +48, Move Silently +30, Search +30, Sense Motive +42, Spell craft +40, Spot +48, Survival +17, Use Magic Device +41
Possessions: +1 dancing vorpal great sword, +1 flaming speed long sword, +1 wounding frost whip, amulet of health +4, belt of giant strength +4, Hide of The Beast
Feats: Devastating Critical and Overwhelming Critical and Fast Healing can be found in the Draconomican
New Artifact: Hide of the Beast
Created by Demogorgon from the hide of a powerful monstrous beast in the depths of the screaming jungle. It acts as +7 hide armor with a max Dex +8, and armor penality of -1, It also grants the wearer the ability to mighty rage 1/day as a 20th level Barbarian, and also gain DR 5/-.