When the other team picks Singed, Jax, Jayce, Udyr, or really anyone else with a reasonably weak early game or that is heavily reliant on AAs and is melee.
Irelia vs Nasus is slightly favored for Irelia. Jax vs Nasus is dead even. Udyr vs Nasus is dead even. Jayce vs Nasus favors Jayce at the start, but once you get enough armor Jayce can't touch you.
Singed vs. Nasus is heavily Nasus favored. The slow keeps singed from getting to you for fling/poison harass, or can let you chase him down, along with the passive life steal mitigating the damage from poison and the ult taking down HP, which is typically the only defense that singed gets.
Whatever you do, never play Nasus vs Olaf. You will feed unless he is an idiot.
Always play passively in lane until at least lvl 9, do not overextend, and try not to push (Often it is best to give up some CS on the first minion wave to ensure the other player pushes).
If you fall behind in Q farm due to them harassing you, do not panic, and try to make it up immediately, focus on not dying and make up for it later when you can (Nasus is still strong without a lot of Q farm).
Always build Philo stone. G/10 is essential for keeping up in gold, as you will be focusing on farming Q and will often miss other CS due to harass by the other player, which puts you down by a reasonable amount, depending on the strength of the harass.
Build as much move speed/hp/resists as you can. Damage is not important, as you can get that from SS farm.
Originally Posted by Pker5256
Meh you can build pretty tanky and still do a lot of damage.
jungle nasus is ok too, lotta' sustain and his W? Perfect ganking opportunities.
False. He suffers from the WW syndrome, he can jungle without taking much damage, but it is incredibly slow, his ganks are lackluster, and he needs the SS farm from laning.