As title asks

Two-bladed sword, dwarven urgosh, orc-double axe

You get strength bonus like a two-hander with the attacks of a dual-wielder. Also get double sneaks, flames, etc....

absolute best would be weasel kukris, although GL finding those. I put my EE run on halt, so idk if those were added as a loot somewhere.

best for effortless DW: longswords for redeemer+perfection

best main hand weapons:
Lion's claw
Redeemer
Blinding light

OK-ish main hand weapons:
Bloodhound(kinda meh, but not awful, and can be grabber pretty soon)
Martyr's blade(decent enchants)

Best(light) offhand weapons:
Allslayer
Steelwind

Sais are ok for a non-crit builds, due to tears of blood+steelwind.

Realistically, everyone just uses allslayer for the most part with whatever decent 1h they focus on and arcane protector in the earlygame, as allslayer need not feat investments to be ok. Another option would be shield bash route.

Double weapons are a trap. There is a grand total of 0 good double weapons in the game and if you are dual-wielding you probably are stacking sneak dice to some extent anyways, so str damage boost won't be valuable and whatever you would gain will be lost due to not using Lion's claw.

OP asked for str build

well duh. stil getting more crit dice is better than getting like 20 extra damage at best. If there wa 18-20/x3 dual weapon I'd be all up for it. As is damn dual weapons just take 5 feats and do less damage than Vanqusher. And something like Redeemer+allslayer would require less feat investments and do better damage just on crit alone even if you lose some flat. After all, stacking STR is the better way, as there are far more STR buffs than dex ones.