Nasus

Strengths

Paying attention to last hitting with Siphoning Strike will have a large impact at the end of a game.
If you're solo, Spirit Fire is a great way to farm a lane. It can be bad if you're in a lane with 2 and you push too far. Find the right balance between Siphoning Strike last hits and AoE farming.
If you have low defenses, people will focus you down even during your ultimate. Try buying some survivability items even in your DPS builds.

Passive · Soul Eater — Nasus drains his foe's spiritual energy, giving him bonus Life Steal.
Q · Siphoning Strike — Nasus strikes his foe, dealing damage and increasing the power of his future Siphoning Strikes if he slays his target.
W · Wither — Nasus ages an enemy champion, decelerating their Move Speed and Attack Speed over time.
E · Spirit Fire — Nasus unleashes a spirit flame at a location, dealing damage and reducing the Armor of enemies who stand on it.
Ultimate · Fury of the Sands — Nasus unleashes a mighty sandstorm that batters nearby enemies. While the storm rages, he gains increased Health, Attack Range, damages nearby enemies, has a reduced cooldown on Siphoning Strike, and gains bonus Armor and Magic Resistance.

A suggested 5-lane lineup built around Nasus, based on hero partnerships and role synergy — not win rate.