Thresh vs Xerath

Open with Flay (E) before Death Sentence (Q): the slow makes the hook much easier to land.

In lane, space out your autos: Flay (E) charges them passively, and the longer you wait between two autos, the more damage they deal.

Don't recast Death Sentence (Q) on reflex: the target is already being pulled toward you, and jumping on them often exposes you for nothing.

Throw Dark Passage (W) toward an ally in trouble before they need it: they can click it to come back to you, with a shield.

Place The Box (R) right after a successful hook: to escape, the target has to break a wall, and the first wall broken slows them and deals full damage.

Keep minions between you and Xerath: Shocking Orb (E) stuns the first enemy hit, for longer the farther it has traveled.

Don't stand still, and change direction often: Arcanopulse (Q) hits a target moving forward or backward in a straight line much more easily.

If you can engage, go in while he charges Arcanopulse (Q): he slows down by up to 50%, and he has no dash to escape.

If you have CC and can reach him during Rite of the Arcane (R), use it: he channels the ult, and interrupting it stops his shots.