If you want TWF, go Ranger. It doesn'T really matter what race you pick so long as it gets a Str bonus, but Longtooth Shifter (PHB II) is a good one (if the DM lets you, Bugbear is another awesome option). Put an 18 in Str, a 16 in Wis, then a 14 in either Con or Dex and a 13 in the other, then pick either Cha or Int to be your dump stat and put a 10 in the other. This is after racial modifiers, so pre-race your pb would look like 16/14/14/13/10/8. Putting a 20 in Str may be tempting, but you'll have to balance it against seriously reduced ability in... everything else. Alternatively, you can swap Wis and either Dex or Con, since this is likely a one-shot and you won't use your Wis much.
Next, choose if you want to be a glass cannon or slightly more defensive. In the former case, take Weapon Proficiency (Bastard Sword). In the latter case, take Armor Proficiency (Chainmail) and wield two longswords instead.
For your powers, Twin Strike is a must. Pick whatever for your other at-will, you'll never use it anyway. For your encounter power, pick Off-Hand Strike from Martial Power. It lets you make an attack with your off-hand weapon as a minor action. For your daily, take Wolf Fang Strike. This will be your big gun, and can reliably take down almost anything in one shot.
After buying two weapons and some armor, you won't have much money left, so you're pretty much done now. Congratulations, you're a mean lean foe grinding machine.