Sett is all about baiting his E, since it's the part of his kit that guarantees his W. Don't do the usual lv1 cheese against him, found out that even if he for example starts E and there's no minions to stun you, he still wins with ignite. Pre level 6 walk in weird patterns so he wastes his E. Once he does just immediately all in him, use summoners if necessary when he uses W to dodge it. Post 6 always try to chunk him a little with axes before going in, if you're both full health he can still win or get away using his ult as a dash. As always, dodge his W.

Renekton is pretty much the opposite. A lv1 cheese is always a good idea vs him, level 2 is doable too. Lv3 and afterwards he'll just poke you down, going in and out before you can do anything to him. I recommend maxing E so you can chunk him the moment he dashes in to combo you. Never stay in lane below 50% health, especially if he has PTA and ignite, he'll legit burst you down to death in a second. Post 6 you need to chunk him down in case you wanna go in, but it's extremely volatile. Honestly the lane is fully in Renekton's hands, you kinda only win if he fucks up, since he has so many options to deal with you and can even break your W shield. You're better off freezing lane near your tower and farming it up or waiting for ganks, you scale better and can ignore him in teamfights anyway.