Super high damage + High Attack Range + Runaan's Hurricane (scale with your ult) = dead squishies.
Dead squishies = no damage = ez win.
It's all about your positioning + patience.

Yo don't fall off behind too far, try to farm up for BOTRK (first power spike), then try to sneakily 1v1 duel their adc when he/she farms alone or farm for Recurve Bow + second tier boots then look to gank mid to get Ultimate Hunter stack + snowball.
You hit your ultra power spike after Infinity Edge, look for team fights after that.
Wait for good opportunity before ulting in team fight, YOU ARE THE ULTRA GLASS CANNON, YOU KILL THEM ALL BEFORE THEY KILL YOU, BAIT THEIR HARD CC.

Pros:
-Carry your teams
-Hyper mega ultra damage
-High risk high reward
-Fun to play
Cons:
-Items dependent.
-Hard to recover if you fall off to hard in lane.
-Very squishy, you get caught you die.
-Requires good movement knowledge, positioning and quick decision making.
-No escape tool
-Lane matchup will either be draw or loose in the first 8 minutes.

High cc aggressive support or hard peeler buffer, you need cc to be able to dish out your ultimate.
Look for high CC tanky teamates who will sacrifies for you, or bait them out and unleash hell at the later part of team fights, your damage is insane.

Q: Use it to sneak up into lane if their bot is pushing tower to deal some free damage, after you had your two first attack speed item (Recurve Bow + Berserker's Greaves) you can surprise fight their adc which usually result in a free kill.
W: Useless lol, use it first when break out of Q invisibility, throw it where they will run if you think they can't 1v1 you.
E: Good abilities to finish off their adc, the range is a little bit longer than what you see. DON'T SPAM IT TO CLEAR MINION WAVES, you won't have enough mana if you overdo it.

You loose in long fight early vs any other adc lol.

Try to push get lv2 first throw W at their face shoot once or twice falls back press E, usually this trade will help you a lot early.
Pre lv 6, if you push your minion a little bits then falls back behind their vision, Q then wait till them AA the minion then start trading like earlier.

You are the hyper ultra shooting machine, your 5 seconds after ulting worths more than their adc's whole life, stay out before team fight and pick a good position that IS NOT SANDWICH-ED BETWEEN THEIR TEAM, wait till them staying together even if that means baiting a teammate of yours to make them confident.