Viktor vs Tristana Mid Matchup
Viktor Mid wins 56.4% of 408 Low Elo games against Tristana Mid, +1.2 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.
How to play as Viktor
Use Hextech Ray(E) to trade from outside Tristana's auto-attack range, and respect the cooldown; her Explosive Charge(E) reaches the same distance as her attacks.
Wait for Tristana to use Rocket Jump(W) before placing Gravity Field(W) and Arcane Storm(R); if she jumps onto you, Exhaust her during the burst window.
Tristana can use Rocket Jump(W) to leave Viktor's Gravity Field(W) or Arcane Storm(R) area if she still has the jump available.
How to play as Tristana
Keep Rocket Jump(W) available to escape Viktor's Gravity Field(W) or Arcane Storm(R) if he casts them before you commit; the matchup discussion describes Tristana jumping out of both zones.
Sources
These notes come from r/viktormains, checked against the champions' abilities.