Is it for a PC or an NPC?
The Frenzied Berserker PrC is basically a smack down by itself. Max out strength with a half-orc and frenzy + rage = insane damage and attack bonus. IIRC frenzy at level 10 is +10 strength and it stacks with rage. Toss in power crit, power attack, a keen weapon, imp. crit and you have insane damage.
Lets see, level 6 barb, level 10 frenzy = Strength of 20+4 level ups +4 item +14 frenzy/rage = 42 str = +16 to hit and +24 damage
A keen +4 greataxe makes his attack bonus +36/+31/+26.
So with power attack 6 he's doing 3d12+102 damage pretty much automatically on one attack, and that's being conservative (no triple empowered bull's strength, no +5 weapon, etc...).
It really wouldn't be unreasonable to imagine he hits will all attacks (+30/+25/+20), so 5d12+170, averaging over 200 damage. And that is nothing unreasonable at all. He doesn't need another character to cast any spells on him, no templates, and no items he couldn't easily have at level 16.
--Berserk Spikey
PS Heck, a +3 speed weapon would increase his damage a lot.