Originally Posted by Ceadeus
if your playing a champ thats reliant on auto attacks to some extent, dont fight him while his dodge is up he likes that because it increase the damage the dodge will do (up to double the amount) keep in mind his dodge also reduces area of effect spells damage.
outside of that there's no much you can do if your not willing to play champs that counter pick him, you might be able to win a trade with him early game if you commit and have exhaust or ignite ready but after level 6 don't count on it
I have got to say, Rengar is OP. Last few matches with rengar I have been fighting, against jax, Jayce, teemo and such. I have won with rengar, it isn't hard it just takes proper ferocity control, proper judgement (Like for instance, if there is a jax that is building tanky, and an ashe that has yet to get to sufficient distance to be safe from you. You play it safe, don't go after the closer one, pop your ulti and go for the squishies.) and proper last hitting, average 3v3 game I end up with close to 200 creeps in 20 minutes.