EEK!
If I were designing a 20th level Army Killer Barbarian I would do him this way
32 point buy
Chump Killa
Human Barbarian 20
Str 26
Int 10
Wis 10
Dex 16
Con 18
Cha 10
Feats
H Improved Toughness
1 Power Blow
3 Cleave
6 Great Cleave
9 EWP Spiked Chain
12 Combat Reflexes
15 Greater Resiliance
18 ?
Gear
Adamantium +5 Breastplate Full Fortification
Boots of Striding and Springing
+5 Animated Heavy Steel Shield
+5 Adamantium Spiked Chain "Slaughter Chain" Intellegent Purpose "Kill Chumps"
Power Cure Mod on Caster 12 per day Haste 6x Purpose Power -- Mass Inflict Light
MW Great Axe
MW Longbow Might Comp +5 Str
Arrows, Lots of Arrows
Infinite Slings
Ring of Sustenence
Amulet of Natural Armor +4
Manual of Gainfull Exercise +2
maunual of Bodily Health +2
Belt of Giant Strength +6
Cloak of Minor Displacement
His AC would be 34 or so -- His HP would be (max l1 avg after) -- 235 he would have a DR of 8 and his spiked chain would do 2d4+15 per blow with 4 blows a round at +31/+26+/+21/+16 meaning he will hit an average of 6 times per round (2 aoo within 10') each resulting in an instant kill -- with its power he can nuke 5 extra per round
Enemies with a longsword or longbow hit on a 20 -- say 1000 arrows equals 50 hits and no damage whatsoever .
I figure ChumpKilla will get 4 atacks a round (the 5 foot guys and the 10 ones with cleaves ) ) that will always hit (except on a 1) and kill -- In addition the Chain will dump a mass inflict light every round getting 10 more guys back of them -- thats 14 per round -- for every 4 glaivemen to get to him he will kill 14 -- in a narrow enough space using the figures below as many as 90,00 men can be downed
Against glaives he would take about 15 points (negate 1 thru 8, 9 does 1, 10 does 2) per 1000 attacks -- Assuming a narrow space it would 15000 glaive men to kill him. However with Slaughter Chain he can be cured of 19 points on average per use -- this is 1200 attack and change -- call it a total of 30,000 men. With Slaughterchain he can kill 36000 men in combat before they down him, tripled for the chains mass inflict -- 108000 men!
Thats more than 1/2 of Dariuses army and by the RAW over 9 million GP worth of gear.
About the only thing he has to fear is heavy crossbows
if heavy crossbows are in play 1000 of the guys can inflict 15 points per 2 rounds and can drop him in 30 rounds or so
Lastly if the miniatures handbook is in play he can a shirt that gives DR 5 -- this will render him invulnerable to all attacks from chumps -- Ouch