Troll Monk 20/Initiate of Draconic Mysteries 10/War Mind 10
"SMAAAAAAAAASH!"
Unbuffed stats:
Str: 26 (36 at level 40)
Dex: 18
Con: 26
Int: 10
Wis: 12
Cha: 4
HP: 580
AC: 30
SR: 30
Feats: Wild Talent, Power Attack, Alertness, Weapon Focus (Unarmed Strike), Improved Crit (Unarmed Strike), Great Cleave, Dodge, Psionic Dodge, Speed of Thought, Improved Ki Strike +4, Improved Ki Strike +5, Devastating Critical, Overwhelming Critical, Fast Healing 1
Skills:
Jump 8
Tumble: 40
Heal: 43
Lore: 8
Discipline: 43
Concentration: 10
Pros: Absurdly high melee damage, high DevCrit DC's, very high HP, regeneration, excellent attack bonus, good saving throws, improved evasion, some spell resistance, immune to poison and mind-controlling effects, very high speed (especially when psionically focused), limited self-buffing, 5% chance to stun on-hit.
Cons: Terrible AC, can be a healing sponge, easily dispellable buffs, no social skills, few skills in general, several blown class features in IoDM, needs a +Wis item to cast some War Mind buffs.
Overview: This is the closest you'll ever get to being The Incredible Hulk in D&D. Trolls are large size, and thus use an increased monk unarmed damage progression table. You do 4d8 unarmed damage as a large level 20 monk. Initiate of Draconic Mysteries ups that to 4d12. Use Expansion (from War Mind) to become Huge sized. Now you do 6d12 unarmed damage. Augment that expansion, and you're Gargantuan sized. Now you do 8d12 unarmed damage. Start as a Huge sized dragon (War Mind again) and use an augmented Expansion, and you're Colossal size. Now you do 12d12 unarmed damage. That's an average of 78 HP per strike without even considering any bonuses. Hawt.
Added on top of that, you've got a +17 BAB thanks to your stint as a War Mind. That's four attacks a round. Add one more for Flurry of Blows. Then another for Haste. Then another for Circle Kick. Then for every one of those, you'll get a free attack against an adjacent enemy, courtesy of Sweeping Strikes. And as if that isn't bad enough, anyone you hit twice in a row will be eating a Rend as well. All that comes together for a minimum of six attacks a round, and potentially up to fifteen, all of which can hit for 70+ HP even when completely ungeared. This character packs an utterly horrifying level of offensive melee power. Team this guy up with strong buffers for maximum lulz, because he enjoys monstrous, monstrous scaling from any +hit he can get.
Variants: Nathzarune Rakshasha can trade off Regeneration, Rend and some physical stats in exchange for better mental stats and some really neat abilities. +6d6 sneak attack sends your unarmed damage even higher, and your spell resistance will be much improved as well. The extra intelligence can be spent on stealth skills to make Hide in Plain Sight really shine. Change Shape allows you to get to large size for use with Expansion.
Zakya Rakshasha are a solid race as well, combining the physical stats of a troll with the spell resistance of a Rakshasha, along with some other goodies. True Strike is a big hit, so to speak, offering you 9 seconds of pure, unmitigated beatdown potential.
Trading Initiate of Draconic Mysteries for Fist of Hextor is another solid choice. You lose some damage, and the dragon form, but gain big (around +5) on +hit in return. This is an especially attractive choice since so many of the IoDM class features are duplicated by Monk acquisitions, and even more so for Nathzarune or Zakya Rakshasha since they already start with Martial Weapon Prof.
Disclaimer: This build is not completely tested in NWN, meaning that it's mostly theorycraft. If the unarmed damage progression has changed in any meaningful way from tabletop, or if there is a limit on how big a PC can get, or if the unarmed damage chart doesn't include very large-sized monks, then some of these results may change in the actual application.