Pain Doll without a doubt. If you see Pain doll at Epic in a shop and don't already have the poison combo. You just buy Pain Doll and sell everything, except hour glass, if you happen to have it. Since any item stealing hour glass procs besides the Pain Doll is just bad. So better to only run 2 items with that build.
Once that is nerfed. We're looking at Ice Axe + Reaper + Face + Mirror + <Insert fast weapon with too high base damage>
Once that is nerfed we're probably looking at bomb + whatever rush/charge items you can find to pair with it. But that isn't all that consistent.
After the new patch dropped I went 10-0 i think it was 5 games in a row? Just being fluid and picking any of Poison/Pain Doll/Weapon spam. To be fair the ladder was filled with absolute garbage builds right after patch. But still. Oh and on the subject of Poison. You don't even need Blade/Portal/Slow or Rush trigger anymore. Just Shout+New uhh, that 4s charge 1s item and that poison gain +4 on rush and that just beats nearly everything on its own.