rengar is pretty broken if you play him correctly, focus on your dirk powerspike as it carries you through the early game, you spike hard with every item aswell but your biggest spike is obviously the IE. constantly look for mid ganks and inlane ganks to the sidelines. if an enemy is hitting your tower on a sidelane they shouldn't ever get away because you can run into the bush and get a double E off. if they flash that's worth don't greed.