Xerath vs Viktor Mid Matchup
Xerath Mid wins 53.0% of 4,517 Low Elo games against Viktor Mid, +1.8 points vs expected, 2-patch window 26.19-26.20.
Researched on LoL patch 26.20. Tips are written to hold at any rank; stats come from Low Elo ranked games up to patch 26.20.
Why Xerath is favored
Xerath's longer-range Q and W let him pressure Viktor from beyond Hextech Ray(E), while Rite of the Arcane(R) can threaten picks around objective fights without Xerath walking into Viktor's range. Viktor can answer with wave control and side-lane pressure, but Xerath's poke and distant follow-up give him an edge when those threats are not respected.
How to play as Xerath
Line Arcanopulse(Q) through Viktor and the wave when possible, then keep pressure on him instead of spending every spell on minions. If Viktor shoves and you leave, he can punish the roam with the wave and plates.
Viktor's Hextech Ray(E) can hit Xerath and the wave from a sideways angle; Xerath's Arcanopulse(Q) is a line shot, so he often has to align Viktor and minions to hit both.
Arcanopulse(Q) and Eye of Destruction(W) reach farther than Viktor's Hextech Ray(E), and Rite of the Arcane(R) lets Xerath fire barrages from far away.
How to play as Viktor
Stand off the minion line so Xerath must choose between poking you and hitting the wave. Use Hextech Ray(E) from an angle to chip him while clearing, and keep moving laterally to dodge Arcanopulse(Q).
Sources
These notes come from r/XerathMains and r/viktormains, checked against the champions' abilities.