Lux vs Yasuo

Start with Light Binding (Q), then Lucent Singularity (E) and Final Spark (R) before detonating the singularity: the root makes sure everything hits.

Slip in an auto after each spell that hits: it triggers Illumination (passive) for extra magic damage, and Final Spark (R) triggers it too.

Cast Lucent Singularity (E) into a brush before walking in: the area is revealed, and a hidden enemy would be slowed.

Cast Prismatic Barrier (W) through as many allies as you can: the wand shields them on the way out, then again on the way back.

Cast Final Spark (R) to clear a wave or secure an objective: it only has a 60 to 40 second cooldown, depending on rank.

Hit him with a cheap attack to trigger the Way of the Wanderer (passive) shield, then start the real trade: otherwise, it absorbs your best damage.

If you have projectiles, save them for after Wind Wall (W): it blocks them all for 4 seconds, on a 25 to 17 second cooldown. Other spells go through it.

Don't stand right behind your minions: each one gives him a target for Sweeping Blade (E), and he gets closer to you with every dash.

Get out of the line of his whirlwind, the third Steel Tempest (Q): without a knock-up, he can't cast Last Breath (R).

Judge his threat by his crit items more than his level: Way of the Wanderer (passive) raises his critical strike chance, so each crit item does more for him.