In order to achieve maximum carry potential with thresh you must go AD top. Be aware of your burst potential when you have completed the blade of the ruined king and the static shiv. Then prepare to carry. Step one is camping bot lane waiting for their adc. They will underestimate you but then you will 2 shot em ez. If that fails stay top all game and xPuk. Its the most basic way to win. In my carrier of Thresh top I have xpeked over a 100 times. All you gotta do is have the team stop the ports then you will win the game and get hated on and called a troll.
I have achieved master tier in 4 days with this build. Started in bronze 3.