Not Updated For Current Season
DISCLAIMER: This build is 99% this build and about 1% my own opinion. I decided to post this build here on mobafire because very few of the Swain guides I've found build him the way I do, which I feel is the most effective method.
The key to playing Pain Train Swain is simple: Swain is a Tank. An AP tank, but a tank nonetheless. Building Swain accordingly will allow you to steam roll teams in a never-ending, unstoppable onslaught of power.
(Also, sorry to anyone else who thought of this name before I did.)