Pantheon vs Nasus

Start your trades with Shield Vault (W): you leap onto your target and stun them, so Comet Spear (Q) can't miss.

Tap Comet Spear (Q) for a short thrust that refunds part of the cooldown, or hold it to throw your spear farther.

Raise Aegis Assault (E) against enemy burst: you ignore damage from that direction, except from towers.

Roam with Grand Starfall (R): you leap from long range onto the chosen area, and the spell instantly readies Mortal Will (passive).

Early on, take a trade whenever he steps up to last-hit a minion: each kill with Siphoning Strike (Q) increases its damage for the whole game.

Freeze the wave near your tower: to farm with Siphoning Strike (Q), he then has to step up and expose himself to ganks.

Once he hits level 6, don't engage during Fury of the Sands (R): for 15 seconds, he gains health and resistances, and his area damage scales with your max health.

In teamfights, if you're ranged, hit him while backing off: he has no dash, only Wither (W), a slow that grows stronger over time.