Viego should focus on skirmishes where his (W) stun can lock down a target and enable resets to snowball fights.
Prioritize river fights with lane priority to leverage reset potential and objective control over Nunu's utility and objective speed.
Jungle Plan
Full clear efficiently then path towards lanes where you can assist in securing the first takedown to trigger resets.
Fight for river Scuttle only when allied lanes have priority to support and avoid Nunu's snowball engages.
Use vision to track Nunu's pathing and counter-invade camps when he commits to ganks or objectives on the opposite side.
Danger windows
Early game river fights without lane support are risky due to Nunu's (W) long-range engage and follow-up CC.
Avoid low-health jungle clears where Nunu can punish with his sustain and gank pressure.
Be cautious during forced smite fights at dragon or Herald when Nunu's (Q) sustain and Smite combo can out-secure you.
Early game
Start with a clear that allows quick access to river Scuttle to contest or secure it before Nunu can capitalize on his fast clears.
Avoid early isolated duels before first item as Nunu's gank threat and objective control are stronger early.
Shadow lanes with priority to counter-gank Nunu's frequent early (W) ganks and prevent his snowball angles.
Power spikes
Level 6 (R) unlocks Viego's execute and reset mobility, increasing his threat in skirmishes; look for fights where one low target can start a reset chain.
First fighter item completion boosts sustained dueling and reset potential, allowing longer fights and better objective control.
Respect Nunu's first dragon or Herald spawn power spike as his (Q) plus Smite secure objective advantage; ward and contest early to deny him free starts.
Win conditions
Convert skirmish resets into objective control by coordinating with lanes that have priority to secure dragon and Rift Herald.
Use (E) camouflage to approach ganks from unexpected angles and capitalize on Nunu's predictable snowball paths.
Deny Nunu free farm and objective starts by tracking his movements and counter-jungling when lanes cannot follow his ganks.
Tip: For Viego vs Nunu & Willump, read overview, trading pattern, and danger windows first for a fast Jungle lane check.