If you don't care how long the fight lasts, the best build in the game is pretty obvious.
1 handed + shield
rank 5 shield
rank 5 bodybuilding
rank 5 willpower
rank 5 man-at-arms
weather the storm
picture of health
You won't even come close to losing. No matter what the fight is, you're only several dozen turns away from victory.
This build no longer functions in the latest patch.
Leech does next to nothing anymore (flat 15 hp on your turn only in combat, does not scale with level/hp), and no longer combos with comeback kid.
Weather the Storm no longer has any effect past level 10 or so, since your gear will cap out your resists at 80.